January 25, 2013. At the European 3D TSV Summit in Grenoble, France, on January 22-23, 2013, imec announced that together with Cadence Design Systems they have developed, implemented, and validated an automated 3-D DFT solution to test logic-memory interconnects in DRAM-on-logic stacks. The solution, based on Cadence Encounter Test technology, was verified on an industrial test chip containing a logic die and a JEDEC-compliant Wide-I/O Mobile DRAM.
Memory-on-logic 3-D stacks offer the possibility of heterogeneous integration with dense low-power inter-die interconnects. Hence, they are among the first 3-D products that will come on the market, enabling next-generation high-performance low-power mobile applications. Recently, JEDEC released a standard (JESD-229) for stackable Wide-I/O mobile DRAMs, specifying the logic-memory interface. Unlike many previous DRAMs, the standard contains boundary-scan features to facilitate interconnect testing. Imec and Cadence have now presented a DFT architecture and corresponding automatic test-pattern-generation (ATPG) approach. It is an extension of their previously announced logic-on-logic 3-D DFT architecture, and it supports post-bond testing of the interconnects between the logic die and the DRAM stacked on top of it.
The solution implemented by Cadence and imec includes the generation of DRAM test-control signals in the logic die and the inclusion of the DRAM boundary-scan registers in the serial and parallel test access mechanisms (TAMs) of the 3-D test architecture. The automated design-for-test solution has been validated on an industrial test chip. The design of the test chip is an interposer-based 3-D stacked IC that includes a silicon interposer base die, a 94-mm2 logic system-on-chip in 40-nm technology, and a single Wide-I/O DRAM rank. The validation results show that the silicon area of the additional DFT wrapper is negligible compared with the total logic die size (<0.03%). Moreover, the test-pattern generation was very efficient (tens of patterns, generated in only a few seconds) and effective (100% coverage of the targeted faults). All 3-D DFT logic in the logic die was automatically inserted with Cadence Encounter RTL Compiler, while the Interconnect test patterns were generated with Encounter Test ATPG.
“This 3D memory-on-logic DFT solution is another big step forward toward market introduction of 3-D-stacked IC for next-generation high-performance, low-power mobile applications,” said Bassilios Petrakis, product marketing director for the Encounter Test product family at Cadence. “Our collaboration with imec has enabled the creation of an industry-leading solution that enhances efficiencies of 3D-IC design for our customers.”
“Teaming up with Cadence enables us to automate the insertion of our DFT circuitry in a given design, and to automate the interconnect test pattern generation. Such automated flows make our technology valuable for the industry. We are confident that we can also handle the DFT features that start to emerge in other 3D memory standards,” said Erik Jan Marinissen, principal scientist at imec.
See related article, “Presentation at European 3D TSV Summit charts road to IC test.”