Wafer-to-wafer bonding pulls off sub-micron accuracy
Ziptronix Inc. and EV Group (EVG) have carried out sub-micron post-bond alignment accuracy on customer-provided 300mm DRAM wafers.
The results were achieved by implementing Ziptronix's DBI Hybrid Bonding technology on an EVG Gemini FB production fusion bonder and SmartView NT bond aligner. This approach can be used to manufacture fine-pitch 3D ICs for a variety of applications including stacked memory, advanced image sensors and stacked SoCs.
The DBI Hybrid Bonding is a conductor/dielectric bonding technology that bypasses adhesives, and includes a variety of metal/oxide and/or nitride combinations. The bond occurs between both the dielectric and the conductive surfaces, which effectively bonds the entire substrate interface area. This allows for room temperature dielectric bonding, low temperature conductive bonding, and finer-pitch interconnect over Cu/Cu or other metal bonding.
The Gemini fusion bonder features automated bond alignment and bonding. The operator loads cassettes with unbonded wafers and picks up the finished substrates. It can be equipped with a variety of different pre-processing modules such as cleaner, IR-inspection, plasma activation chamber.
Figure 1: The Gemini fusion bonding equipment has been optimised to achieve consistent sub-micron post-bond alignment accuracy. Source: EVG
Meanwhile, the SmartView NT bond aligner offers a proprietary method of face-to-face wafer-level alignment, which is said to be the key to achieving the required accuracy in multiple wafer stacking. This system has been combined with the GEMINI FB, resulting in a fully automated platform where surfaces can be prepared simultaneously for bonding, electrical connectivity and mechanical strength.
Figure 2: The SmartView NT's optics and tables. Source: EVG
Pitch scaling on next-generation 3D technologies is expected to continue for many years to come. Fine-pitch hybrid bonding is already in use in high-performance 3D memory products, and has been announced for high-volume manufacturing of 3D image sensors.
DBI Hybrid Bonding can be used at the die or wafer level; however, wafer-level bonding enables a great cost benefit by bonding all the die at once. With much of the processing for technology taking place at wafer scale, there is the added benefit of low cost-of-ownership.
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