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Through wafer interconnects (TWIs) enable vertical stacking of integrated circuit chips in a single package. A complete process to fabricate TWIs has been developed and demonstrated using blank test wafers. The next step in integrating this technology into 3D microelectronic packaging is the demonstration of TWIs on wafers with preexisting microcir...
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... photomasks were designed for the TWI bridge process. Fig. 3 is the cross-sectional view of the pMOS transistor. Fig. 7 shows a composite layout diagram of a single pMOS transistor prior to TWI processing (four masks total). Fig. 8 shows the same composite layout with the three additional mask layers re- quired for the TWI bridge process superimposed. For simplicity, the 50-m TWIs were located in the center of each 100-m bond pad on the test chip. The IMVs are much smaller (10 m was chosen due to the wet etch processing being used) and could be placed anywhere ...
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This paper presents a review of the wafer-to-wafer alignment used for 3-D integration. This technology is an important manufacturing technique for advanced microelectronics and microelectromechanical systems, including 3-D integrated circuits, advanced wafer-level packaging, and microfluidics. Commercially available alignment tools provide prebondi...
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... Three-dimensional (3D) chip stacking packaging technology is dominating the state-of-the-art electronic products, especially portable electronic products. [1][2][3][4][5][6][7] To stack up several chips, direct interconnection is too difficult to be carried out. Instead, stacking up chips with interposers 8 will be easily implemented through an architectural design of re-distribution lines (RDLs). ...
Three substrates, Al2O3, AlN and glass, were directly metallized by copper electroplating using Al-doped ZnO (AZO) as an adhesive and conducting layer between these substrates and the electroplated copper layer. The AZO was synthesized in sol-gel solution, where the Al content in the AZO sol-gel was 2 at.%. Because the AZO is a conductor that can be etched by an acidic solution, copper patterns can be directly electroplated on these substrates coated with the patterned AZO. The AZO patterns went through dry film coating, pattern formation and dry film removal process steps. Two direct copper pattern electroplating processes were proposed in this work, where one process could protect the patterned AZO from being undercut because AZO layer was patterned first and then copper was directly electroplated on the patterned AZO; the other process could not do so because copper was electroplated on the AZO layer and then both the electroplated copper layer and the AZO layer were simultaneously patterned. The copper electroplating solution must be alkaline; otherwise the AZO coated on the substrates would be etched in an acidic copper electroplating solution.
... This technology is an essential component when integrating devices using a 3-D approach. Jozwiak et al. investigated three different process sequences for the integration of pMOSFET devices using through wafer interconnects (TWIs) [32]. Their " bridge process " involved the fabrication of TWIs from the wafer front side following the deposition and patterning of the bond pad metal layer giving the fewest concerns with regard to the integrity of the pre-existing circuitry. ...
... Following processing of the TWIs, these devices were tested from the back side of the wafer and the performance was similar to the performance before processing of TWIs. Change in performance was an issue when the TWIs were fabricated from the wafer front side before insertion of the bond pad and when TWIs were processed from the wafer back side [32]. Using TSVs, Taklo et al. combined a fast detector sensor in a 3-D package with low parasitic capacitance to generate a radiation detection system with very fast response time [33]. ...
... 3 -D PACKAGING for micro-electro-mechanical systems (MEMS) has drawn more and more attention during the past few years. For a complete system, packaging is often 75%-95% percent of the cost, and determines the overall size of the device since the package size may be significantly larger than the functional die [1]. Therefore, in many cases, a compact device relies on the shrinkage of the packaging, rather than the chip itself. ...
Wafer level Cu-Sn solid liquid interdiffusion (SLID) bonding of interconnects was achieved by bonding two-layered Cu/Sn structures to each other. The bonded interconnects were investigated by mechanical, electrical and microscopic techniques. The Cu-Sn SLID interconnects were created by wafer-level bonding at 260 °C. The bonded interconnects show shear strength of 45 MPa and a resistance of the order 100 m� .Am ajor advantage of the Cu/Sn to Cu/Sn bonding scenario is to avoid the dynamic wetting of molten Sn to Cu, and simply replace with a liquid to liquid integration. Furthermore, the Sn overflow problem in a Cu/Sn SLID system was successfully addressed by designing a margin of 15 μm at the Cu pads to tolerate any Sn spreading. The uniformity requirement for electroplated Cu-Sn layers, which is crucial for achieving successful wafer- level bonding, is discussed. This wafer-level Cu-Sn SLID bonding process is a promising technique for 3-D assembly and packaging.
... Several works have been dedicated to the development of techniques for stacking integrated circuit chips, each made by conventional 2D electronics. 1-3 These methods consist in standard 2D integrated circuit ͑IC͒ fabrication of circuits on silicon, or silicon on insulator, wafers; IC chips are successively thinned and stacked up and, through wafers vias, 4,5 are provided for electrical interconnections. These so-called 3D integration technologies consist essentially of the fabrication of standard 2D circuits that are successively packaged in a particular way ͑stacked up͒. ...
Electrical conduction in chaotic media near the percolation threshold is investigated by means of Monte Carlo techniques. The main target is to demonstrate the possibility of modulating the conduction of a chaotic film by means of lateral gate electrodes fabricated in the plane of the film. Exponential variations in the conductivity due to the modification of random paths in the chaotic film can be exploited for the realization of devices with high on/off ratio. In this work it is demonstrated that despite the chaotic conduction driven by charge hopping between localized sites, an almost deterministic behavior can be obtained for suitable site concentrations. Transistors based on this concept could be realized on different layers, on the same substrate, with technologies similar to those actually used for conventional integrated circuits: this would make possible an effective three-dimensional integration of devices and circuits.
... Through-wafer interconnections (TWI) (otherwise known as through-silicon vias) are a critical and enabling technology for 3D wafer-level packaging. Compared to conventional planar feed-through interconnections, TWI offers the advantages of smaller package size, higher connection density and lower resistance [1]. The fabrication of TWI has three requirements: (1) production of a via through the wafer, (2) introduction of a conductive pathway and (3) isolation of this pathway from the rest of the wafer. ...
Through-wafer electrical interconnection is a critical technology for advanced packaging. In this paper, a novel capillary-effect-based solder pump has been proposed and analyzed, which could produce interconnects through and between silicon dies. The principle of this pump is to use the surface tension of a molten solder, introduced in the form of balls, to drive sufficient material into a deep reactive-ion etched hole to form a through-wafer conductive path. The solder pump structure uses unwettable through-wafer holes of different diameters together with wettable metallization on two dies to provide the pressure differential and flow path. Using multiple feed holes and a single via hole complete through-wafer interconnects are demonstrated.
... The current can be blocked by a capacitor placed between the probe and the integrated circuit (Donaldson et al 2003, Grayden andClark 2006), but most amplifier designers reject this technique as being impractically large. However, the advent of high-permittivity dielectrics (Venkateshan et al 2007) and stacked or 'three-dimensional' integrated circuits (Ayoub et al 2007, Jozwiak et al 2008 may restore the blocking capacitor to common practice. ...
Significant progress has been made in systems that interpret the electrical signals of the brain in order to control an actuator. One version of these systems senses neuronal extracellular action potentials with an array of up to 100 miniature probes inserted into the cortex. The impedance of each probe is high, so environmental electrical noise is readily coupled to the neuronal signal. To minimize this noise, an amplifier is placed close to each probe. Thus, the need has arisen for many amplifiers to be placed near the cortex. Commercially available integrated circuits do not satisfy the area, power and noise requirements of this application, so researchers have designed custom integrated-circuit amplifiers. This paper presents a comprehensive survey of the neural amplifiers described in publications prior to 2008. Methods to achieve high input impedance, low noise and a large time-constant high-pass filter are reviewed. A tutorial on the biological, electrochemical, mechanical and electromagnetic phenomena that influence amplifier design is provided. Areas for additional research, including sub-nanoampere electrolysis and chronic cortical heating, are discussed. Unresolved design concerns, including teraohm circuitry, electrical overstress and component failure, are identified.
We present the electrodeposition of copper (Cu) nanocomposites with a high content of carbon nanotubes (CNTs), and evaluate the mechanical and thermal properties of the nanocomposites. Two kinds of multi-walled CNTs (MWCNTs), thermally-annealed at 1200oC and 2600oC, are pretreated in a polyelectrolyte solution to show positive charges on their surfaces and added into a sulfuric Cu electroplating solution. The weight fractions of the MWCNTs in the electroplated composites are 5.3 wt% and 2.8 wt%, respectively. The Young’s moduli of the composites are approximately 1.2 times and 1.1 times greater than that of a pure Cu thin film, and the coefficients of thermal expansion (CTEs) of the composites are reduced to be 77% and 85% of the CTE of the pure Cu film, respectively. The mechanical strengthening and thermal expansion reduction are found in the composite. These results show that the nanocomposites would be used instead of Cu thin film for interconnect applications.
We present a novel approach for high-aspect ratio low resistance Thru-Wafer Interconnects for Double- Sided (TWIDS) fabrication of Micro Electro Mechanical Systems (MEMS). The interconnects are formed by etching blind via holes in the handle substrate of an SOI (Silicon on Insulator) wafer, followed by filling the holes with copper, using sonic-assisted seedless copper electroplating process. This technique does not require additional conductive layer deposition, but utilizes a highly doped silicon device layer as a seed. The donut-shape gaps are etched around the copper filled vias to provide interconnects insulation. We introduced the fabrication process and characterized the performance of interconnects. Experimental analysis of an array of 22 interconnects demonstrated that the resistance values as low as 160 milli-Ohm can be achieved. Parasitic capacitance of interconnects is analytically calculated and the distortion of the MEMS resonator transduction spectrum is predicted using an equivalent circuit model. Signal amplitude and phase distortion due to the parasitic capacitance are estimated to be 1.15 dB and 5.96 deg, respectively, for the optimum 60 um diameter via with 35 um insulating gap. The method presented is compatible with an in-house folded MEMS fabrication process and may enable 3D folded TIMU (Timing Inertial Measurement Unit) structures with thru-wafer interconnects. Copyright © 2014 IMAPS - International Microelectronics Assembly and Packaging Society All Rights Reserved.
We present in this paper an alternative Through-Silicon-Via approach that can meet the new requirements of Si package. In this wafer level packaging scheme, a thick silicon interposer (200 to 300μm) is directly reported on a PCB. In 200mm Si wafers, we made a two steps TSV composed of two vias: a top via and a bottom via. The top via is etched with DRIE (diameter 60μm, depth 180 μm, Aspect Ratio = AR>3), and insulated with high temperature dielectric. After dry film lithography, the TSV is partially plated with Cu limiting the process costs (short plating time, no CMP) and the stress inside the TSV. After temporary carrier bonding, the wafer is backgrinded so that 15μm remains below the bottom of the main TSV. Backside lithography and DRIE process create the bottom via (four different diameters: 10-20-30 and 40μm) to contact main TSV. A final backside Cu plating of the opening completed the process. This via bridges the gap between via-last (AR<2) and via-middle (AR>7) and combines high temperature process from via-middle and low-cost processing from via-last. The mechanical simulations show that this "TSV bridge" has reduced residual stresses inside the TSV. Our electrical measurements exhibit an average single TSV resistance below 10mOhms with excellent yield (∼95% on Kelvin and 82 TSV chains), and low contact resistances (4.7×10-9 Ω.cm2) extrapolated on 4 different contact diameters. This 200μm deep TSV seems therefore very promising for low-cost thick interposer applications.
