“We showcased our 4D NAND technology that will become the standard for the next generation.”

SK hynix’s Head of NAND development, Jungdal Choi, shared his thoughts after attending the Flash Memory Summit 2022 (FMS 2022), where SK hynix clearly demonstrated its competitiveness in cutting-edge technology in both DRAM and NAND, which dovetail nicely to lay the foundation for its future.

Flexing its technological muscle at FMS 2022, SK hynix is set to become a leader in ICT technology development. The current 4D NAND technology is recognized as an industry standard, thanks to its developers’ dedication and ceaseless efforts. The company also plans to continue supporting technological innovation that will help set the next-generation standard of 4D NAND technology.

Image 1. Jungdal Choi, Head of NAND Development, delivers his keynote speech at the Flash Memory Summit 2022.

The Newsroom team hosted an FMS debriefing session, meeting with Jungdal Choi (Head of NAND Development), Jumsoo Kim (Head of S238 NAND), Jaesung Sim (Head of NAND QLC), Woopyo Jeong (Head of NAND Design), and Keumhwan Noh (Head of NAND PE C&R). Read on to hear snippets of the conversation, where the execs share their views on how they know SK hynix is poised to become the undisputed leader in NAND technology.

Showing the world 4D NAND’s core competitiveness

SK hynix was a key participant in FMS 2022, according to Jungdal Choi, Head of NAND development, where it introduced various products and new technologies including a 238-layer 512Gb (gigabit) TLC^* 4D NAND (238-layer NAND). SK hynix’s 4D^2.0 technology, which overcame the limitations of vertical stacking, was of particular interest.

*Triple Level Cell (TLC): NAND Flash products are categorized into Single Level Cell, Multi Level Cell, Triple Level Cell, Quadruple Level Cell and Penta Level Cell depending on the number of information (unit: bit) contained in a single cell. That a cell contains more information means more data can be stored within the same extent of area.

Choi, who spearheaded SK hynix’s presence at the event, explained the meaning of the participation and achievements as follows. “FMS 2022 raised SK hynix’s status through our differentiated NAND technology. It was a valuable opportunity to inform the world of SK hynix’s technological direction and of our 4D NAND core competitiveness,” Choi stated, giving an overview of the company’s goals and achievements at the event.

Image 2. Jungdal Choi, Head of NAND Development, discusses the core competitiveness of 4D NAND with other key members of the NAND department.

Q. What is the core competitiveness of 4D NAND?

Jungdal Choi NAND’s core competitiveness depends on securing the industry’s most stringent management in terms of scheduling, cost, quality, and performance, as well as developing competitive products with differentiated and unique technology. In 2018, we succeeded in commercializing our own industry-first, 96-layer 4D NAND, achieving the highest technological level in the industry. Additionally, based on our expertise accumulated from developing the 96-layer NAND, we developed the industry’s first 128-layer, 176-layer, and 238-layer NAND, gaining a technological advantage in the process.

The core technologies of 4D NAND that have led to these results are largely represented by three categories:

Sideway Source is a technology that horizontally connects the source, which is the electrons pathway. This technology lessens the dependence on the vertical structure of cell stacking and alignment issues between sources, and as a result, it is easy to secure yields.

All PUC (Peri Under Cell) is a technology that places the entire peripheral circuit (Peri.) under the cell. Thanks to this technology, chips size can be further reduced, and production efficiency is maximized.

Advanced CTF is a technology that stores electric charges in a CTF (Charge Trap Flash), which is an insulator, rather than a floating gate, which is a conductor. Compared to the floating gate storage method, cell area per unit can be reduced and read/write performance can be improved.

Image 3. Peri. Under Cell (PUC): A technology that maximizes production efficiency by placing peripheral circuits under the cell array.

Image 4. Charge Trap Flash (CTF): Unlike floating gate, which stores electric charges in conductors, CTF stores electric charges in insulators, which eliminates interference between cells, improving read and write performance while reducing cell area per unit compared to floating gate technology.

Q. Which products and technologies received most of the audience’s attention?

Jungdal Choi There was a lot of interest in the world’s highest and smallest 238-layer NAND flash. In addition to QLC, there were many questions about floating gate-based PLC and a software solution that can maximize the performance of CXL (Compute Express Link)^*. People were very interested in the introduction of highest quality evaluation from customers and SSD products based on ultra-high-layered NAND. In addition, we are shaping the direction of technological innovation and serving as a leader in the NAND industry by defining next generation 4D NAND with 4D^2.0 technology, which realizes both high capacity and performance while overcoming the limitations of cell stacking. I was able to feel firsthand that SK hynix’s technology and products are garnering interest.

^*CXL: A next-generation interface for efficient utilization of high-performance computing systems. As a memory solution that can increase bandwidth and capacity cost-efficiently, SK hynix recently developed a 96GB CXL memory sample based on DDR5 DRAM.

Jungdal Choi These progressive and innovative technologies were achieved thanks to close collaboration with business partners and rooted in customer satisfaction. Most importantly, I believe that this success is based on the VWBE^* initiative and the ambitious spirit among SK hynix employees, or “hy-gineers”, as we call them. The reason we were able to develop our proprietary technology and grow rapidly was thanks to our employees’ efforts and passion. We will not be satisfied resting on our laurels and will strive to continue to grow together.

^*VWBE: Voluntary and Willing Brain Engagement. It is one of the employee values emphasized by SK Management System, or SKMS.

Surprise launch of 238-layer TLC 4D NAND, emphasis on technological superiority

As Choi pointed out earlier, the 238-layer NAND garnered a great deal of attention at the event. Jumsoo Kim, the head of S238 NAND who led the product development, said, “We garnered unprecedented attention as our chip size was reduced by more than 30% while applying advanced technologies such as the All PUC structure.”

Kim also emphasized that the product has technological advantages in cell writing speed (tPROG, the Programing Time), input/output speed (I/O speed), reading power efficiency, and bit growth.

Image 5. Jumsoo Kim, Head of S238 NAND, explains the 238-layer TLC 4D NAND’s technological superiority.

Q. Could you please explain the features of 238-layer NAND in a little more detail?

Jumsoo Kim When it comes to SSD performance, the most important factors are cell writing speed and I/O speed. Cell writing speed improved by 10% and this product also boasts speeds of 2.4 Gb per second, which is 50% faster than the previous generation, while reading power efficiency has also been improved by 20%. This is a product that meets market demand in a situation where customers are turning to low-power products.

Meanwhile, the products are also extraordinary in terms of bit growth: SK hynix can expect 34%-bit growth thanks to a dramatic reduction in the chip size.

QLC/PLC development is also on an upward trend… targets the future NAND market

SK hynix made a splash at FMS by unveiling 176-layer QLC NAND, 238-layer QLC NAND for mobile applications, and 192-layer QLC NAND adopting floating gate technology. In particular, the 176-layer 1Tb (terabit) QLC NAND doubled the I/O speed (1.6Gbps) compared to the 96-layer 1Tb QLC NAND and the read and write performance improved by 42% and 18%, respectively. “Our world record definitely stood out in the QLC area as well,” said Jaesung Sim, Head of NAND QLC, as he introduced the major products unveiled at the event.

Image 6. Jaesung Sim, Head of NAND QLC, explains the major products unveiled at FMS, including the 176-layer 1Tb QLC.

Q. What is the current development status of the 238-layer mobile QLC NAND and 192-layer QLC NAND?

Jaesung Sim We expect to do a full-fledged development for the mobile QLC. Accordingly, SK hynix is developing a 238-layer mobile QLC NAND. The 192-layer QLC for cSSD and eSSDs is also being developed by using floating gate technology with excellent multi-bit retention characteristics. Development of PLCs with a 25% increase in bit density per cell compared to QLC is also on the way as we speak.

Q. What efforts are you making to increase the number of stacks and bit density?

Jaesung Sim SK hynix pre-emptively developed 4D NAND technology and applied multi-row^* technology, while rapidly changing the technological direction to multi-bit such as QLC and PLC. As a result, the company soon boasted the highest number of cell stacks and bit density in the industry. This was possible due to the quality maintenance process as well as design and testing technologies.

^*Multi-row is a technology for continuously arranging multiple cell-stacked structures, similar to placing multiple apartment buildings next to each other in an apartment complex.

Introducing 4D^2.0 technology while looking ahead to the next-generation technology standard

As one might assume from Sim’s explanation, SK hynix is continuously developing next-generation technologies that break through technological limits. This contributed to the introduction of the 4D^2.0 technology.

4D^1.0 reduces chip sizes by placing the NAND peripheral circuit (Peri.) under the cell area. With 4D^1.0, chip sizes are reduced but the number of cell stacks must be increased. Although this has the advantage of being able to implement high density within a fixed area, the disadvantage is that the stacking technology could reach its limit. SK hynix solved this problem by horizontally increasing the cell density, a technological concept known as 4D^2.0. According to Woopyo Jeong, Head of NAND design, this technology is expected to be the next-generation standard.

Image 7. Woopyo Jeong, Head of NAND Design, explaining 4D^2.0 that overcomes the stacking limit by increasing horizontal density.

Q. What is the core technology of 4D^2.0?

Woopyo Jeong Multi-Site Cells (MSCs), which store data by dividing existing cells into two smaller cells via micro fabrication is the key, because we can expect to reduce the number of cell stacks while increasing cell density. For example, suppose that 6-bit data is stored in one cell. This can be implemented by combining the two signals 0 and 1 into 2⁶=64 different (voltage) states. However, it is very difficult to create 64 states in a limited voltage range.

However, if we use MSC technology, which combines two cells, we can implement a total of 64 (8×8) states by creating 3 bits per cell, that is, 2³=8. As a result, the 3-bit MSC secures the same capacity as a 6-bit cell, which is difficult to implement using a single cell.

Q. What will the future of the NAND market that 4D^2.0 will create look like?

Woopyo Jeong If vertical stacking and size reduction are repeated, cell quality inevitably deteriorates. Therefore, in the future, it will be difficult to increase data capacity using only stacking technologies. However, 4D^2.0, which utilizes MSCs as the core to horizontally increase density, can overcome this limitation. This is expected to become an industry standard in the future.

As technology becomes more sophisticated, quality is our top priority

As NAND technology advances, it will be difficult to secure the best quality. SK hynix also faced numerous difficulties during the development process and had no choice but to work harder at improving quality. Accordingly, Keumhwan Noh, Head of NAND PE C&R, emphasized quality as a top priority, saying, “The excellent quality of SK hynix will continue in the future.”

In a recent quality evaluation survey of major mobile and SSD companies, SK hynix’s 128-layer and 176-layer NAND products ranked first. Noh argued that the stabilization of the 4D NAND development platform and mass production was the main reason, along with the significantly reduced number of defects. SK hynix is currently developing new products based on stabilized processes and is planning to introduce various quality improvement technologies and solutions.

Image 8. Keumhwan Noh, Head of NAND PE C&R, reveals challenges related to NAND quality improvement.

Q. What are the biggest issues related to quality and the challenges ahead?

Keumhwan Noh As the number of cell stacks continues to increase, the gap between cells will become narrower. Therefore, it is highly likely that defects in the cell region will increase. To respond to these issues, SK hynix is seeking a wide array of measures such as strengthening NAND Design for Manufacturing (DFM)^* initiative, reinforcing inline management, source quality advancement using AI machine learning, and controlling defects by utilizing solution algorithms.

^*DFM (Design for Manufacturing): Design in consideration of the manufacturing environment, which makes a reliable product or a design for productivity.

SK hynix plans to upgrade its products in line with technological trends, mass-produce 238-layer NAND in the first half of next year, and consecutively release mobile-oriented products, cSSDs and eSSDs. In order to respond to high-capacity demand, the company is preparing 238-layer 1Tb QLC products, strengthening multi-bit storage capacity from QLC to PLC, and preparing the next-generation technology of 4D^2.0.

After the session, Jungdal Choi said, “Looking back at the ICT industry over the past 10 plus years, only companies with their own unique technology were able to secure their status as top global technology companies. We will maintain our competitiveness through successful ramp-ups (yield improvement) of 4D^1.0 and innovation with our proprietary 4D^2.0 NAND technology.”

The post FMS 2022 Reflections: SK hynix Poised to Become Next Generation 4D NAND Leader first appeared on SK hynix Newsroom.

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SK hynix’s DRAM business has been evaluated as a driving force that has led the company’s rapid growth in recent years and as a key business representing the company. Although SK hynix’s DRAM business ranks second in sales and global market share, it is fiercely competing for the No.1 position in terms of product quality and technology. The key organization leading this high level of technology is the DRAM Development organization. This organization is in charge of developing core products and various derivative products for each technology state and commercializing them through internal certification and customer certification within a given time.

As the Head of the organization responsible for an important duty, Seon Yong Cha of DRAM Development is walking toward the future step by step with confidence, instead of being overwhelmed.

“We always try hard to be the best, but we are staying in second place in terms of scale in reality. If we secure the ‘best technology’, our overall competitiveness including scale will increase, so we are thinking hard to figure out how we can take the ‘first place in technology’.”

As effort comes with achievements, SK hynix is continuing its growth this year, focusing on high-density memory and HBM2E.

“As its name suggests, high-density memory has high density, which means that it must have both good quality and yield for the high density. SK hynix has secured sufficient competitiveness, as well as an impressive market share. In particular, among DRAM products, the quality of server DRAM is the most important, and SK hynix maintains a high share of the overall server products including high-density memory. (1st place with 40% of market share in the first half of 2020, according to market research institute Omdia)

HBM2E products are also leading the market. Both quality and performance are currently recognized by customers, and we expect to continue this trend in the future. Also, we are giving shape to plans to strengthen the competitiveness of mobile and graphic related products.”

Cha also expressed his anticipation for the automotive business. Although SK hynix’s market share in the automotive semiconductor field is not yet high, he expected that meaningful results can be achieved if the company uses its long-accumulated know-how for memory semiconductor technology.

“In the semiconductor business, competitiveness in the automotive sector is crucial. This is because the quality requirements for products in this sector are very high. The automotive business is expected to upgrade SK hynix’s overall product quality and production system. If this business is well established, it can serve as leverage for the quality of all other DRAM products. In addition, it will open a new path for the DRAM business as a premium product lineup.”

Regarding the business situation in the second half of this year, some forecast that “the company’s performance will be in a bearish trend, as customers’ DRAM inventory is piled up”. On the contrary, others expect that “the performance will improve next year due to shortages in supply”. Also, the recent global business environment which became more volatile suggests that there are more things to consider in business.

“To respond to changes in the business environment, we are working to establish a solid cooperative relationship with our customers. Although many different variables are affecting the business, as the demand for memory semiconductor continues, we will do our best not to miss out a market we can target.”

Semiconductor industry is a typical “cycle industry” where boom and bust repeat. Because the industry is also sensitive to external variables, it is necessary to constantly monitor the global situation and market conditions to respond proactively. One of the important tasks is to reduce the impact of the industry situation and external variables and lay the foundation for operating the business stably. Cha is currently preparing for this as well.

“When considering the nature of the semiconductor industry, securing cost competitiveness means the strength to withstand changes in the external market environment. Recently, a task force (TF) to secure cost competitiveness was formed to establish a plan. We are working on many action plans to secure the competitiveness for No.1.”

“Limits Exist to be Overcome”: Cha as an Analytical Strategist

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As some say that the technology gap within the leading group of the DRAM business has almost disappeared, it is most important for SK hynix to solidify its technological leadership as a company belongs to the leading group. In terms of securing core technology, SK hynix has achieved some great results by introducing the concept of “platform”, starting from 1xnm (first-generation 10 nm-class products). Platform means developing a technological system that can be applied for a long time to many generations, instead of developing a technology that can be applied only to one generation.

“Adopting the platform concept has the advantage of reducing trial and error when developing the next generation of technology that shares the same platform, even though it costs for investment when the initial platform changes. Thanks to this advantage, we were able to successfully and efficiently develop various products from 1xnm (first-generation 10nm-class products) to 1ynm (second-generation 10nm-class products), then to 1znm (third-generation 10nm-class products).”

The next step after securing the core technology is to apply this technology to multiple products of the same generation to secure competitiveness in the performance aspects of each product, such as power, speed, quality, and high density. While this process by SK hynix has not been entirely satisfactory, Cha was confident that it is now changing.

“Since this year, we have subdivided the product performance into eight areas. We have established and are pursuing plans for each area to secure the competitiveness necessary for each area. The technology level for each performance area might be relatively different from each other, but we aim to pursue the highest level of technical competitiveness in all areas within the next few years.”

It is getting more difficult to continue Moore’s Law¹ in the semiconductor industry. There is also a prospect that the limit of the miniaturization of DRAM is approaching in the industry. Nevertheless, Cha expressed his firm determination to overcome the limits with tenacity, rather than preventing the possibility of development due to the “limits”.

“I don’t want to describe it as a ‘limit’. In the past, there were times when people thought 100nm was the limit, and then 20nm was considered to be the limit. Nevertheless, overcoming the limit every time is the process of DRAM development until today. The current difficulties are also barriers to be overcome, which means that we have not reached the limit. I believe that innovative technologies will soon be developed to break through the barrier which is currently considered as a limit.”

The structure of the semiconductor industry is also changing rapidly. While PC manufacturers were the main customers in the past, various types of IT companies such as mobile companies and internet data center operators are newly included in the customer group, diversifying the requirements.

In addition, the recent semiconductor industry is showing a wide range of change, and there is a prospect that a complete change can be made in the future, not only in terms of the environment of competition, but also the competitors themselves. Cha emphasized the necessity of identifying this rapidly changing trend of the semiconductor industry and responding quickly.

“In the past, when new technology was developed, the profits were made by reducing the cost of core products which has a high proportion in sales. Now, however, it is more like making profits through using the premium by securing a wide range of lineups of derivative products that will meet the different needs of customers. In fact, the share of derivative products in DRAM sales has grown significantly compared to several years ago.

In more and more cases, customers are demanding customized memory products, so it is not enough to make a good product according to the defined specifications. The process of planning products that customers need and commercializing them has become more important. It is time to preemptively establish a system to respond to these changes in the market.

In fact, there are risks in the customized memory business. This is because if the commercialization plan falls through during the development process, you will have to bear as much damage as the resource used. Nevertheless, I think we should keep trying. Whatever changes are made to the market, the key is the customer. In the future, the business should proceed in the direction of improving customer value, even if it carries some risks.”

If such change keeps accelerating, it is expected that more driving force will be given to the establishment of a “product-oriented system” that SK hynix is currently focusing on. DRAM Development is also preparing the system in line with this trend.

“The product-oriented system is a concept that started with a question, ‘how will we reflect the customer needs that are becoming more diverse, from the product level to secure competitiveness?’. In the past, when a core technology’s level was raised, you could just use that technology to make most of your products. In recent years, however, the importance of derivative products has increased, so different and a lot of element technologies are now required for each product. Also, it is necessary to prepare the element technologies in advance. For this reason, from this year, we are establishing and following a roadmap that determines the element technologies needed for each product and defines schedules for development and verification.”

The diversification of customers also means that collaboration with customers has become important. Due to the recent COVID-19 outbreak, however, communication with customers is not easy. What kind of efforts is SK hynix making for smooth customer relationship, in this changing environment?

“As customers’ systems become more complex and sophisticated, the process of evaluating and analyzing data at the time when our products were mounted on the customer system, and finding and solving defects in advance is becoming more important. In particular, in the post-COVID-19 era when the ‘contactless’ environment will be generalized, it is also necessary to prepare a customer communication system suitable for this.

To realize this, SK hynix is establishing a system that allows real-time online testing and analysis, without having to dispatch engineers to the field. We will continue to think more about strengthening collaboration with our customers in the future.”

A Warm-hearted Mentor for Members

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Since taking charge of DRAM Development, Cha has been putting a lot of effort into improving the organizational culture. One of the representative cases is that he streamlined the internal certification process after a technology is developed, and this reduced the stress of the employees caused by various issues.

Internal product certification is one of the core tasks of DRAM Development. This is a very important task to keep the delivery schedule promised with customers. It takes over a month for one internal certification process, and if it fails, it needs more time and effort, which means more stress for employees. Cha thought that it is necessary to increase the success rate for certification first to improve work efficiency.

“First, what I suggested as a goal was to significantly increase the success rate of the first certification. To achieve this, I asked Process Integration (PI) to work to dramatically increase the wafer yield in the first test. Also, Product Engineering (PE) worked to reinforce the pre-test quality inspection system. Product Management Office (PMO) responsible for organizing the overall certification, materials, and development process, has been reinforced with stronger authority, so that the entire development process can be managed more thoroughly. Thanks to these efforts, the certification success rate this year has improved significantly.”

In the second half of this year, he focused on creating a new vision for DRAM Development from the perspective of the employees, and shared it with them recently. The new vision is “Experts group who continuously grow through No.1 brand products”. It shows his hope that the members feel proud of making “No.1 brand products”.

“Visions we’ve seen so far were more about the organization. It was a way to set the future orientation of the organization, not members, and to think about how to achieve that goal; however, as it is difficult to identify the organization with the individual members, I thought, ‘Will the members feel thrilled with this kind of vision?’

What I was trying to do this time was to create a vision that makes the members’ hearts beat. I shared the vision with the members, but it hasn’t been completed yet. I’d like to continue to communicate with the members to create a vision that can be shared with everyone.”

Cha enjoys meeting and chatting with the members. He often meets in small groups of four to five people and listens to them. This is because it allows him to understand other members and find various ways to support them. It is not as often as before due to COVID-19, but he plans to increase contact points with the members in the future.

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Lastly, the newsroom team asked Cha to define himself, as one of leaders at SK hynix.

“I want to become a leader who put the head together to get an answer with the members. Rather than being a difficult leader asking for a well-organized report on the solution when a problem arises, I’d like to be a friendly leader who can think of ideas together and solve the problem together.”

¹Moore’s Law: Moore’s law is the observation that the density of microchips doubles every 24 months.

The post “Dreaming of the Best DRAM”, Toward the No.1 in Technology: Head of DRAM Development Seon Yong Cha first appeared on SK hynix Newsroom.