On the evening of September 4, the weekly public lecture of the CAD Alliance Zhangjiang Forum was held at the Alliance Member Activity Center.
The Semiconductor CAD Alliance Zhangjiang Forum series of public lectures aims to invite experts from various subfields to share in-depth insights on specific technical topics (such as new ideas, new technologies, industry pain points, etc.) and engage in thorough discussions with attendees, providing a high-quality content sharing and learning platform for practitioners. Topics revolve around EDA environments and tools, CAD and IT technologies, AI technologies, information security, digitalization, and intelligence.
This lecture invitedDr. Zou Feng, Product Manager of Yanchip Microelectronics, Peking Universityto present the topic “Embedded NVM Technology Under Advanced Processes“.
Lecture Content:
This presentation is divided into two parts: the first part focuses on the current state of storage technology and the application prospects of RRAM, while the second part shares the latest progress and achievements of Peking University and Yanchip Microelectronics in RRAM technology and productization.
1. Storage Technology and RRAM Applications
1. In the current system-level storage architecture, there is a significant performance gap between DRAM and SSD, and this “storage wall” has become a key bottleneck restricting the continuous development of computer architecture.
2. In high-performance SoC chips, there is a lack of mature embedded non-volatile memory (eNVM) technology below the 28nm advanced process node, which severely affects the evolution of chip design and applications.
3. With the rapid rise of emerging industries such as artificial intelligence and the Internet of Things, the market demand for high-performance SoC continues to grow, placing higher requirements on on-chip storage in terms of speed, power consumption, and reliability.
4. As a new generation of storage technology, RRAM has advantages over traditional Flash in terms of faster speed, lower power consumption, higher density, lower cost, and stronger reliability, with broad application prospects.
5. Leading chip manufacturers worldwide have already adopted eRRAM as embedded storage technology, achieving initial penetration in the domestic DDIC industry.
2. Peking University& Yanchip Microelectronics RRAM Achievements Sharing
1. Yanchip Microelectronics’ technology and core team originate from Peking University, possessing the capability for independent research and development across the entire chain from materials to devices to arrays to chips, forming a complete, open, and sustainable evolution of the RRAM intellectual property system.
2. Achieved risk production on domestic 40nm/28nm process platforms, breaking international integration density records at the same node, and verified through automotive-grade reliability testing.
3. Yanchip Microelectronics has developed a standalone 28nm RRAM storage chip, which offers faster read and write speeds and lower power consumption compared to traditional Nor Flash, and supports XIP functionality, effectively reducing the SoC’s dependency on on-chip Cache capacity.
4. Peking University and Yanchip Microelectronics have completed the design of an RRAM-based compute-in-memory AI prototype chip and conducted preliminary validation, achieving multi-target tracking and tracking demonstrations. This compute-in-memory architecture can achieve an area efficiency of 1.4 Tops/mm² and an energy efficiency of 12 Tops/w, fully demonstrating the potential of RRAM in the field of intelligent computing.
Q&A Section
1. What are the advantages of embedded RRAM IP? Why is the 90nm node marked in gray?
Answer: First, at advanced process nodes of 28nm and below, traditional eFlash can no longer be supported, and new non-volatile storage technologies must be adopted. In contrast, RRAM has the following outstanding advantages:
ØCost and Process: Among the current new storage technologies, RRAM has the lowest implementation cost and is fully compatible with CMOS processes, requiring only the addition of two layers of Mask to complete, without the need for additional complex procedures.
ØPerformance and Reliability: Under the same process conditions, RRAM is faster and consumes less power compared to Flash, has superior high-temperature characteristics, and naturally supports radiation resistance.
As for the 90nm node being marked in gray, the main reason is that there are already mature eFlash solutions at this process, and RRAM as an emerging technology does not have a significant advantage in maturity. As a startup, Yanchip Microelectronics currently focuses strategically on the 40nm, 28nm, and below advanced process nodes to form a differentiated competitive advantage against traditional Flash.
Of course, from a technical perspective, RRAM can also support traditional process nodes such as 90nm. Since it is a back-end process, it only requires the addition of two layers of Mask to achieve, and in small-batch application scenarios, it still has a certain cost advantage compared to Flash, so if customers have needs and the Fab supports it, we can also provide corresponding IP solutions.
2. Is it possible for RRAM to achieve the capacity and performance of SSDs in the future?
Answer: Currently, SSDs mainly use NAND Flash as the underlying storage medium, which is essentially a type of “large-capacity storage product.” In contrast, RRAM has more potential for future storage applications in entering the “storage-class memory (SCM)” emerging track, becoming a new storage layer between DRAM and NAND Flash.
To meet the application requirements of storage-class memory, the following key indicators must be achieved:
ØRead and Write Latency: Achieve microsecond level;
ØErase and Write Endurance: Exceed 100,000 cycles;
ØSingle Chip Capacity:Above 1Gb;
ØEnergy Efficiency: Read and write power consumption lower than DRAM.
From the existing results, RRAM has shown significant advantages in latency, endurance, and power consumption, but it still needs breakthroughs in single chip capacity. To achieve a capacity above 1Gb, further improvements in storage density (>600Mb/mm²) are required, which relies on the development of RRAMmulti-level storage technology and 3D array structures.
Yanchip Microelectronics is actively conducting related research, laying out high-density RRAM, multi-level characteristics, and 3D stacking technology. We believe that with technological evolution, RRAM is expected to approach or even exceed SSDs in terms of capacity and performance, providing a new storage-class memory solution for the industry.
3. Can you elaborate on how RRAM has advantages over Flash in terms of electromagnetic interference resistance?
Answer: From the perspective of storage mechanisms, RRAM is a non-volatile storage technology based on resistance change, while Flash relies on charge storage in floating-gate transistors. RRAM stores information through different conductive filament states in the dielectric layer, being sensitive only to the voltage applied at both ends, thus having low sensitivity to spatial electromagnetic interference. In contrast, the floating-gate structure of Flash is prone to charge leakage, threshold voltage drift, and data flipping under strong electromagnetic interference, affecting the stability and reliability of stored data.
Therefore, from the principle and structure, RRAM inherently possesses stronger electromagnetic interference resistance, making it particularly suitable for applications requiring high reliability (such as automotive electronics, aerospace, industrial control, etc.).
4. Will adding RRAM IP affect the overall yield of the chip?
Answer: Introducing embedded eRRAM does not significantly affect the overall yield of a SoC chip. Its integration belongs to the back-end process, requiring only a small number of photomasks, with no changes to the front-end logic circuits, and has been verified through process platforms such as 40/28nm, showing stable overall yield performance.
It should be noted that the eRRAM unit itself may have defects in conductive filament formation or stability, but this is not fundamentally different from embedded Flash and other storage technologies, as even in mature processes, eFlash cannot achieve 100% error-free performance. The industry typically ensures reliability through redundancy repair, bad block masking, and ECC error correction mechanisms, so the introduction of eRRAM will not become a yield bottleneck and can fully meet the needs of mass-produced chips.
Manufacturer Acknowledgment
This lecture was supported by technical experts from 【Yanchip Microelectronics (Shanghai) Co., Ltd.】.