January 29, 2019
Last fall, two outstanding scientists from DuPont Electronics & Imaging were named recipients of the 2018 Pedersen Medal. This award is named in honor of DuPont’s Nobel Laureate, Charles J. Pedersen, and recognizes individuals for outstanding technical achievements that have had great impact and delivered significant value for the Specialty Products Division of DowDuPont.
Hua Cui, Ph.D., technical fellow, DuPont Electronics & Imaging, was recognized for developing EKC™ 580 and EKC™ 590, innovative products that have delivered previously unachieved cleaning performance and highly selective etching on titanium nitride (TiN), replacing traditional solvent-based solutions with aqueous formulations.
Bainian (Brian) Qian, Ph.D., senior research scientist, DuPont Electronics & Imaging, was recognized for technical leadership in creating the Ikonic™ series of chemical mechanical planarization (CMP) pads that offer the right balance of performance and cost of ownership.
Both technologies are used in semiconductor fabrication processes. In this interview, we talk to Cui and Qian to learn more about their technical accomplishments and their thoughts on innovation.
Q: How do customers benefit from these technologies?
Cui: Our EKC technology business has a long history of providing interconnect cleaners to the semiconductor industry. Interconnect fabrication requires cleaners to effectively remove unwanted residues from substrates after reactive-ion etching.
EKC™ 580 and EKC™ 590 are enablers for copper interconnect fabrication in the manufacturing of system on a chip (SOC) devices. SOC chips provide the core functionality for smart phones and other mobile devices. Logic device scales are constantly shrinking – where the 28nm technology node process was once the norm seven years ago, now 10nm devices are in production. EKC™ 580 and EKC™ 590 can deliver new levels of cleaning performance and highly selective etching to meet these increasing fabrication demands.
EKC™ 580 has been adopted in the manufacture of SOC devices in popular smart phones in the marketplace today, and EKC™ 590 will be used for an upcoming next-generation device.
Qian: With the Ikonic™ series of CMP polishing pads, we’re helping our customers continue pacing with Moore’s Law by packing more transistors into smaller spaces, increase processing power, and improve energy efficiency. For context, five years ago, the iPhone A7 processor had around 1 billion transistors.1 The newest iPhone A12 processor now packs nearly 7 billion.2 So does Huawei’s Kirin 980. 3
Fabricating sophisticated chips requires more CMP steps, and more sophisticated CMP consumables. Our Ikonic™ pad families were initially designed to deliver high yield and low defects for our customers at advanced technology nodes—in this case, 10nm and beyond. But now they’re being adopted more and more for mature technology nodes, because they can also increase throughput and reduce cost of ownership. For example, the Ikonic™ 4250H pad gives about 50% higher removal rate in tungsten polishing.
Q: How did these technologies get their start?
Cui: With the industry focusing on advanced electronic devices, technology nodes continue to shrink. Beginning with the 28nm fabrication process, we saw a TiN mask integrated into back-end-of-line (BEOL) patterning, requiring etch residue removal and TiN mask removal. Oxidation is a required mechanism for removing TiN mask, and oxidation also removes the residues.
Our customers produce chips at very high volumes, and most customers prefer to use chemistries that have already been proven in the fab. For EKC™ 580 and EKC™ 590, we chose hydrogen peroxide as the oxidizer because this was already used in other fab processes and was already accepted by customers. However, peroxide is unstable, and our peroxide approach is a departure from traditional recirculating solutions due to the limited stability.
This new formulation approach was met with resistance during the development stage, yet, our solution is so effective that it has now been adopted globally. Hydrogen peroxide is added to EKC™ 580 and EKC™ 590 at point of use.
Qian: We started working on what would become Ikonic™ 2000 in 2011. Our R&D team was trying to create a new platform to fill a critical gap in our product portfolio, because soft polishing pads based on traditional pad chemistry had texturability limitations.
The Ikonic™ 2000 series was designed for multiple polishing applications in advanced technology nodes, including copper barrier, High K Metal Gate, Through-Silicon Via, and tungsten buffing. Since our initial launch in early 2013, five products in that family have been commercialized: Ikonic™ 2010H, 2020H, 2040H, 2060H, and 2120M.
At the same time, we began working on the Ikonic™ 4000 series, in an effort to break traditional removal rate and defectivity trade-offs for advanced CMP polishing in Shallow Trench Isolation, Self-Aligned Contact, silicon, silicon-germanium, bulk copper, cobalt, and tungsten bulk. Four new products—Ikonic™ 4140H, 4250H, 4121H, and 4101H—have been commercialized in the Ikonic™ 4000 series since the family’s launch in early 2015, with more products in active customer engagements.
Q: Do you continue to be involved with these technologies now that they are commercial product offerings?
Cui: Yes, I serve as the technical expert for EKC™ 580 and EKC™ 590, and act as a trusted advisor for our customers, including traveling to customer sites when appropriate. We initially developed EKC™ 580 and EKC™ 590 for the fabrication of logic devices, and I’m now working on developing applications for memory devices, such as DRAM and NAND.
Qian: I also continue to work as the focal point for both the Ikonic™ 2000 and 4000 series, interfacing with our raw materials, manufacturing, quality, applications, and customer-facing teams, to provide technical support to improve product quality and consistency and win customer engagements by matching customers’ needs with our product performance.
Q: Will these materials be able to be used into the future? What will be needed for the next generation of materials for semiconductor fabrication?
Cui: Both EKC™ 580 and EKC™ 590 were developed for advanced manufacturing processes. EKC™ 580 is today used in 28nm, 14nm and 10nm technology nodes, and EKC™ 590 was designed for the 7nm technology node. For the next-generation 5nm technology node, the smallest dimension copper interconnects will be replaced with cobalt interconnects. Tungsten plugs will be replaced with cobalt plugs. Across the industry, we’re seeing a trend toward replacing copper interconnects with cobalt throughout the device architecture.4
Qian: From my perspective in the CMP space, the trend continues to be that materials need to meet both more specific and more diverse requirements.
Our Ikonic™ series of CMP polishing pads are being used in 10nm and 7nm technology nodes and are extendable to more advanced manufacturing processes. But looking even beyond that, in addition to more stringent product quality and consistency, we’ll need complete CMP system solutions tailored to meet the diverse and unique requirements of each polishing application.
Q: What does it mean to you to have an innovation mindset?
Cui: To me, this means being creative, always having an open mind and thinking outside the box. It is also critical to have an intimate understanding of the problem domain. Finally, you must be persistent. EKC™ 580 and EKC™ 590 would not have happened had we stuck to conventional wisdom.
Qian: It means bringing new thinking to what you’re working on daily and continually challenging the status quo. Our CMP polishing pads already lead the industry in terms of quality and consistency, yet I still work closely with our manufacturing, quality, and engineering science teams to identify approaches to even further improve the quality and consistency of our products. I am also working closely with our customer-facing teams to identify any potential performance gaps and provide technical guidance from a system approach for CMP solutions.
Q: Who do you admire or look to for inspiration?
Cui: Someone I admire is Steve Jobs. He was truly a visionary, and an evangelist of technology that changed our world.
In an early interview, Jobs was quoted as saying, “I’ve always been attracted to the more revolutionary changes. I don’t know why. Because they’re harder. They’re much more stressful emotionally. And you usually go through a period where everybody tells you that you’ve completely failed.”5
This kind of thinking led to revolutionary products.
Qian: I have to say I admire our manufacturing team—they work day in and day out to deliver our commitment to our customers, making our products consistently and meeting demand volumes. New products wouldn’t mean anything if we aren’t able to deliver them both at high volumes and with consistency.
Q: What are you working on now?
Cui: The technologies I’m working on that I can disclose are cobalt interconnect product offerings for logic devices. I’m also exploring memory applications and some opportunities in the packaging segment. But there are also some other emerging technologies that you’ll just have to watch for in the future!
I also provide product development and formulation mentoring to our young scientists to position them to better meet the evolving requirements of our customer’s applications.
Qian: In addition to continuing to collaborate on the Ikonic™ product lines, I’m starting to focus more on mentoring for our newer scientists and engineers, as they grow and take the lead on our next major innovations. I’m also working on quality initiatives for our raw materials, CMP system solutions that pair pads and slurry, and some Ikonic™ 4000 extensions to further reduce defectivity and conditioning sensitivity.
Figure 1: Advances in photoresist technology have enabled the scaling of integrated circuits over the past 50 years. Many of these solutions were introduced by Dow Electronic Solutions. Dow’s first-to-market solutions are indicated on this chart.
The Pedersen Award Medalists were recognized at DuPont’s innovation conference, TechCon, on October 10, 2018. Pictured are the four medalists: Richard T. Fox, Ph.D., principal research scientist, Safety & Construction (left); Hua Cui, Ph.D., technical fellow, Electronics & Imaging (2ndfrom left); Michel Renaud, M.Eng., regional design CAE leader, Transportation & Advanced Polymers (4th from left); and Bainian (Brian) Qian (right), Ph.D., senior research scientist, Electronics & Imaging. In the center is Alexa Dembek, Chief Technology and Sustainability Officer, DowDuPont Specialty Products.