Redundant elements in memories have long been used to enhance the manufacturing yield of silicon devices. Although redundant elements allocated during manufacturing tests are fully tested, unallocated elements remain untested. To increase device reliability, allocation of unused redundant elements and in-field testing may become necessary throughout the lifecycle of a device. In other words, all redundant elements must be tested during manufacturing to prevent the allocation of a defective spare in the field. This paper presents a novel hardware architecture and manufacturing test flow required to systematically test all redundant row elements and preemptively identify defective ones. This solution ensures that only reliable unallocated spare elements remain available for in-system repair.

Error Correction Codes (ECC) in current designs typically serve two purposes. For emerging non-volatile memory types (NVM), such as embedded magnetoresistive random access memory (eMRAM), ECC is necessary to counter the probabilistic behavior of the NVM, rendering the combined NVM/ECC a deterministic memory again. The second and much more prominent usage of ECC today is to protect the system against transient faults in the memory, here typically for SRAMs. On the other hand, new defect types for such emerging memories and new technology nodes may exceed reasonable costs of conventional row and column repair. To improve yield, users explore ECC as an option to augment the repair capability of the memory. This paper brings such an augmentation into a standard memory test and repair flow. It allows a user-defined, post silicon trade-off of using all or parts of the corrective power of the ECC for yield improvements and/or for system protection. Experimental results underline the very low area cost of this augmentation.

Embedded non-volatile RAM technology, and in particular Magneto-resistive RAM (MRAM), continues making great progress in read/write speed and cycling endurance, now rivaling traditional memory technologies. This advancement together with their low-energy consumption and non-volatility opens huge application markets. While stand-alone MRAM products are already being deployed, the first pilot applications for embedded MRAM are just starting to emerge. The availability of Design-for-Test (DFT) tools is key in the transition from low-volume technology exploration and pilot projects to high-volume production. In this paper we explore a new aspect of a Memory Built-In Self-Test (MBIST) tool for eMRAM, namely Error Correcting Code (ECC)-aware test and repair technology. This new MBIST capability provides the ability to make in-system, user-programmable trade-offs concerning the eMRAM repair resources. Having extra control over the repair resources in turn increases both manufacturing yield as well as the longevity of the product in its application.

Techniques for sharing memory repair logic amongst memories are described. The techniques allows reducing silicon area and loading time of repair information upon power up. The impact on yield is predicted using two different methods based on defect density and clustering or past silicon experience.

A tile based design methodology consists of developing design blocks that are inserted in design layouts by placing blocks next to each other, making a tile-to-tile connection by abutting corresponding physical signal lines at the border of the tile. Very large systems can be easily and rapidly developed by seamlessly integrating tile elements in the layout. Further, the ease of top-level integration underlines the advantages over a bottom-up approach. However, this tile-based approach is incompatible with traditional DFT tools, which were created to work in accordance with the bottom-up design methodology. This paper outlines some of the obstacles to overcome, to support a truly tile-based DFT methodology. We describe here a working solution for a large production design, underlining a successful implementation of a tile-based Memory Test methodology.