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electrical and electronics
Micro-chip
Chip with micro-hotplate for self-healing and sustainable electronics
Heat treatment, also known as annealing, is a common step in the semiconductor fabrication process. A build-up of radiation-induced localized charge within the semiconductor and insulator alters local field distribution, threshold voltage and leakage current. NASA's patent-pending technology implements an annealing process on a system level directly on a chip for annealing defects and improving device performance with heating done in the laboratory. The annealing may be performed inside an oven, or upon a hotplate. A system on microheater provides defect annealing capability for recovering bulk trapped charges and interface states. The healing starts simply by heating the chip in a process that can be compared to that of humans immune system - something capable of detecting and quickly responding to any number of possible assaults in order to keep the larger system working optimally. A microheater is monolithically integrated on the backside of a generic Complementary Metal Oxide Semiconductor (CMOS) chip for an on-chip annealing system (left Figure 1(b)). Compared to a stacked microheater, the monolithic integration reduces the die profile, which accordingly enhances the heating power efficiency and heating/cooling rates, which was verified experimentally and numerically. The self-healing microheater is controlled by a temperature feedback circuit to maintain the desired temperature. All circuits under the treatment are unbiased in order to avoid any side effects on normal devices. A control circuit block is programmed to monitor a device parameter shift such as the threshold voltage on the same chip in order to determine the need for treatment. A control circuit triggers the micro hotplate and senses the temperature to adjust the target temperature and duration. The microheater and the system-on-chip are fabricated separately and stacked into a single package, which can be implemented on any arbitrary commercial-off-the-shelf device as a generic approach.
materials and coatings
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Copyright by RPXTech. Permission to use freely granted by RPX Tech via email from Steve Sennet on 11/17/2020, attached.
Self-Healing Aluminum Metal Matrix Composite (MMC)
This materials system is comprised of an Al metal matrix with high-performance SMA reinforcements. The combination of the unique matrix composition and SMA elements allow for this material system to self-repair via a two-step crack repair method. When a crack is present in the matrix material, the MMC is heated above the SMA's austenite start (As) temperature. This initiates shape recovery of the SMA, pulling the crack together as the SMA reinforcements return to their initial length. Concurrently, the increased temperature causes softening and liquefaction of the eutectic micro-constituent in the matrix, which enables the recovery of plastic strain in the matrix as well as crack filling. Combined with the crack closure force provided by the SMA reinforcements completely reverting to their original length, the MMC welds itself together and, upon cooling, results in a solidified composite able to realize its pre-cracked, original strength. The research team has demonstrated and tested the new materials. The team induced cracks in prototype materials based on Al-Si matrix with SMA (NiTi) reinforcements and demonstrated the recovery of tensile strength after healing. Data from tensile and fatigue tests of the samples before and after the fatigue crack healing shows a 91.6% healing efficiency on average under tensile conditions.
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