Contact resistance

About: Contact resistance is a research topic. Over the lifetime, 15262 publications have been published within this topic receiving 232144 citations. The topic is also known as: electrical contact resistance & ECR.

Mechanisms underlying the unstable contact resistance of conductive adhesives

Abstract: Conductive adhesives have been successfully applied to hybrid circuits and die-attach applications. More recently they have become the exclusive bonding techniques for flex interconnections to LCDs and driver ICs (chip on glass). Additional applications for bonding surface mount devices as well as flip chip components on rigid and flexible printed circuits are being explored. In surface mount applications, surface mount conductive adhesives (SMCAs) are an environmentally friendly alternative to Sn/Pb metal solder. In addition, SMCAs offer many other advantages over Sn/Pb solder in surface mount applications, including high pitch capability, mild processing temperature, and fewer processing steps. However, one critical drawback of the current SMCA technology is its unstable contact resistance with non-noble metal finished components. The contact resistance of the assembly usually shows substantial increase over time particularly under high temperature (85/spl deg/C) and high humidity (85%RH) conditions (so called 85/85 conditions). Several possible mechanisms including metal oxidation and electrochemical corrosion have been suggested in the literature. However, prior work has not confirmed the exact mechanism responsible for unstable contact resistance. The focus of this study was to identify the underlying mechanism that results in the unstable contact resistance phenomenon of the current SMCAs. A contact resistance test device consisting of metal wire segments and conductive adhesive dots was developed for this study. Based on the results of this systematic study, electrochemical corrosion has been identified as the underlying mechanism responsible for the observed unstable contact resistance phenomenon of conductive adhesives.

AlGaN/GaN High-Electron-Mobility Transistors Fabricated Through a Au-Free Technology

Abstract: This letter reports undoped AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated with a Si-CMOS-compatible technology based on Ti/Al/W ohmic and Schottky contacts. The use of ohmic recess is key to reduce the contact resistance of this Au-free metallization below 0.5 Ω·mm. Comparison of HEMTs fabricated on the same wafer with and without ohmic recess shows that the recess provides a tenfold reduction in contact resistance, resulting in a fivefold lower forward voltage drop at IDS = 100 mA/mm. The reported Au-free AlGaN/GaN HEMT fabrication technology provides similar performance (i.e., contact resistance, leakage current, and breakdown voltage) than state-of-the-art Au-based AlGaN/GaN HEMTs and can be used in standard Si fabs without the risk of contamination.

Switching behavior in II-IV-V2 amorphous semiconductor systems

Abstract: The electrical characteristics and switching behavior of amorphous ternary semiconducting CdGeAs 2 were studied under DC and AC conditions. The samples tested were fabricated as as-quenched bulk compounds, roller splat-quenched ribbons, and Ar-sputtered thin films. Vapor deposited Ag, Au and Al behaved similarly as electrical contacts while the commercial Ag-paste electrodes revealed variable contact resistance. The threshold electric field of ribbon sample was ∼ 5 × 10 3 V/cm, smaller than ∼ 1.5 × 10 4 V/cm for the sputtered thin films. The electrical band gap of amorphous CdGeAs 2 was determined to be 1.2 eV (n-type). The “forming” process was believed to occur during the first switching cycle whereby highly conductive amorphous channels formed through the width of the samples. The effects of current on switching were investigated and shown not to be significant. The response time for switching decreased approximately exponentially with the applied voltage. The thermal assisted electronic model was postulated for the OFF-ON transition in these materials.

Low-Resistance Electrical Contact to Carbon Nanotubes With Graphitic Interfacial Layer

Abstract: Carbon nanotubes (CNTs) are promising candidates for transistors and interconnects for nanoelectronic circuits. Although CNTs intrinsically have excellent electrical conductivity, the large contact resistance at the interface between CNT and metal hinders its practical application. Here, we show that electrical contact to the CNT is substantially improved using a graphitic interfacial layer catalyzed by a Ni layer. The p-type semiconducting CNT with graphitic contact exhibits high on-state conductance at room temperature and a steep subthreshold swing in a back-gate configuration. We also show contact improvement to the semiconducting CNTs with different capping metals. To study the role of the graphitic interfacial layer in the contact stack, the capping metal and Ni catalyst were selectively removed and replaced with new metal pads deposited by evaporation and without further annealing. Good electrical contact to the semiconducting CNTs was still preserved after the new metal replacement, indicating that the contact improvement is attributed to the presence of the graphitic interfacial layer.