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.
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.Bonding of metal surfaces is extensively used for MEMS sealing, power devices, heat dissipation or 3D interconnections. For these applications, techniques such as thermo compression, with or without eutectic alloys or adhesives layers, bumps with low temperature solders or direct bonding are extensively implemented techniques. 1-7 Moreover, for More Moore and More than Moore applications, low temperature bonding and metal bonding are becoming the main drivers of the latest developments. As copper is the main metal used for CMOS interconnects, a high-density Cu interconnection between layer structures, is expected for future three-dimensional integration of electronic devices fabricated on the basis of different technology/ design concepts. In this paper, 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 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. Hybridization Techniques ReviewCopper is the most (compared to other possible bonding metals) promising candidate for 3D integration technology either for TSV filling or interstata hybridizing. The main reasons of this choice is the widely use of copper in semiconductor device industries and the cost of ownership. On the other hand, the choice of the metal bonding technique is still an open question. Bonding anneal temperature, duration of the annealing, need of an underfill, size and pitch of the interconnect pads, availability of the technique for wafer bonding or die bonding are key parameters of the final choice. The main studied bonding techniques can be divided into two groups: with and without thermal compression.Bonding with a compression force: Diffusion bonding.-The thermal compression bonding is a well known technique. 8-10 Wafers or dies are pressed together with a controlled force in a bonding tool, while heating is applied (400 C) to allow the bonding diffusion mechanism. Thanks to the compression force, the surfaces roughness is not a limiting factor as the surface asperities are deformed at the bonding interface, therefore surfaces with a roughness in the range of 5 nm can be used. Copper oxide should be avoided or removed right before ...
In part 1 of the current study of haptic displays, a finite element (FE) model of a finger exploring a plate vibrating out-of-plane at ultrasonic frequencies was developed as well as a spring-frictional slider model. It was concluded that the reduction in friction induced by the vibrations could be ascribed to ratchet mechanism as a result of intermittent contact. The relative reduction in friction calculated using the FE model could be superimposed onto an exponential function of a dimensionless group defined from relevant parameters. The current paper presents measurements of the reduction in friction, involving real and artificial fingertips, as a function of the vibrational amplitude and frequency, the applied normal force and the exploration velocity. The results are reasonably similar to the calculated FE values and also could be superimposed using the exponential function provided that the intermittent contact was sufficiently well developed, which for the frequencies examined correspond to a minimum vibrational amplitude of ∼ 1 µm P-P. It was observed that the reduction in friction depends on the exploration velocity and is independent of the applied normal force and ambient air pressure, which is not consistent with the squeeze film mechanism. However, the modelling did not incorporate the influence of air and the effect of ambient pressure was measured under a limited range of conditions, Thus squeeze film levitation may be synergistic with the mechanical interaction.
Standing Lamb waves in vibrating plates enable haptic interfaces. If the out‐of‐plane displacement of these waves exceeds 1 µm at frequencies above 25 kHz, a silent friction modulation can be created between a human finger and a vibrating plate. A fully transparent friction‐modulation haptic device based on a piezoelectric thin film is demonstrated. The antisymmetric Lamb mode induced at 73 kHz allows for a functional performance that fulfills all conditions for practical use. Out‐of‐plane displacement reaches 2.9 µm when 150 V unipolar voltage is applied. The average transmittance of the whole transducer reaches 75%. The key points of this technology are: 1) a thin HfO2 layer between lead zirconate titanate film and substrate that prevents chemical reaction between them; 2) the efficient integration of transparent indium tin oxide electrodes and solution‐derived piezoelectric lead zirconate titanate thin film onto optical‐grade fused silica; and 3) the use of a transparent insulating layer made of SU‐8 photoresist.
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