A Fault-Tolerant and High-Speed Memory Controller Targeting 3D Flash Memory Cubes for Space Applications

In this work, we develop a new 3D flash memory cube architecture that integrates multiple flash dies and their logic controller in a unique and optimized fashion for space applications. In our Loaf-of-Bread (LOB) configuration, flash dies are standing up and bonded laterally instead of the conventional pancake-style vertical die stacking. Our LOB allows the flash dies to be bonded without the use of through-silicon-vias and micro-bumps. Instead, we insert a redistribution layer in between two adjacent dies to bring the IO signals to the bottom, where a logic controller die collects the IOs from all flash dies and coordinates the communication with an off-cube host processor. Thus, our LOB configuration allows the users to form flash memory cubes using off-the-shelf 2D flash dies and complete the integration at a packaging house instead of a fab. A key element in our LOB flash cube is the logic controller architecture that supports fault-tolerant and energy-efficient operation of the cube. We develop the controller architecture and validate the functionality using C++ emulation and FPGA prototyping. Compared with a state-of-the-art space-grade flash memory module, our system shows a 20X bandwidth improvement in a smaller form factor along with a 25X better ratio of density per volume.