ViaForm®: Transforming a new technology into an industry standard
ViaForm® plating solution | ViaForm® NExT™ plating solution
As copper gained ground in the semiconductor industry in the late 1990s, it was clear that, while use of this new metal offered higher conductivity and better miniaturization, the implementation would require new chipmaking processes and materials. To address this need, ATMI leaders developed a relationship with Enthone Inc., an established electroplating company, to bring to market a complete approach to copper electroplating that quickly emerged as the industry standard.
The Problem: A promising, but untested, new technology
When the possibility of copper as a back-end interconnect first emerged in the early 1990s, ATMI and Enthone each recognized that this new technology had enormous potential-but it also presented a number of challenges. From issues of electro-migration and internal stress to the integration with CMP (chemical-mechanical planarization), the act of depositing copper wires which are 1/1,000th the diameter of a single human hair on semiconductor chips was full of challenges.
Even larger questions hovered: While copper electroplating was not itself a new technology, what was the best way to integrate it into the semiconductor industry's manufacturing processes? And finally, would one solution meet the needs of different chip manufacturers or would each solution need to be customized?
As ATMI scientists investigated these problems, they soon felt that they understood the chemistry of the copper solution, as well as its impact on film properties and performance. At the same time, they recognized that building their own process from the ground up would be too time-consuming, given the industry's clear need.
One of ATMI's strengths is to know when to go it alone and when to collaborate. Turning copper interconnect from an intriguing idea into a practical technology would clearly involve leveraging the expertise of a partner, so CEO Doug Neugold, then ATMI's president, sought out Enthone, a longstanding leader in electroplating solutions for a wide variety of applications.
"We knew that, with 75 years of experience in electroplating for everything from microelectronics to jewelry, Enthone would be just the partner we needed," said Neugold. "It had become obvious that, for ATMI, starting from scratch was not the best use of our time or resources."
From this collaboration, combining Enthone's mastery of electroplating with ATMI's deep experience with the particular needs of the semiconductor industry, the question of copper interconnect found its resolution in the ViaFormŽ plating technology.
The Solution: Chemistry that fits the needs of each customer
It quickly became clear that a workable copper interconnect technology would have to be highly customizable. By involving customers in the development process, ATMI found a range of opinion about what level of impurity should be introduced with the copper. By altering the chemistry of the proprietary organic polymers in the acid copper plating solution, ATMI and Enthone were able to manipulate the properties of the resulting film to meet the individual parameters set by different chip manufacturers.
ATMI's close relationship with a large semiconductor customer gave ATMI and Enthone the ability to test the ViaForm plating solution against real-world parameters and modify the technology based on these results. These interactions ensured that the final product would reflect real customer needs.
They also gave ATMI a new insight into how the composition of the organic components could solve process problems, such as the difficulty arising from CMP. The efficiency of CMP is closely tied to the topography of the copper film: the more planar the surface, the less likely that too-aggressive CMP will produce dishing and erosion.
Initially, the industry saw the need for only two organic components a suppressor and an accelerator in the plating solution in order to achieve void-free deposition. Enthone discovered that adding a third component, a leveler, reduced mounding over high-density features and produced a markedly more planar surface. This immediately set the ViaForm plating solution apart from the technologies of competitors, which were reformulated to include a leveler once the ViaForm solution's superior performance had been demonstrated after its initial release in June 2000.
The Result: Higher yields and a new industry standard
It didn't take long for the semiconductor industry to realize that the ViaForm plating solution offered a flexible and highly effective way to introduce copper interconnect technology into their manufacturing process. The technology's success was both dramatic and measurable. Huge gains in chip reliability and large jumps in yield encouraged quick and widespread adoption, making the ViaForm plating solution the new industry standard within just a few years.
"The importance of plating chemistry in enabling copper interconnects can't be overstated," said Ben Lochtenberg, ATMI vice president of marketing. "By understanding and advancing the material science of electroplating, we're able to meet the industry's challenges."
Today, most copper interconnect for 130nm chips employs first-generation ViaForm technology, which can be extended to use in 90nm and (in many cases) 65nm chips as well. A second-generation ViaForm ViaForm NExTTM plating solution is already in production. This technology will answer the demands of tighter geometries and thin, discontinuous seed at 65nm and below.
Work has begun on the third generation of the ViaForm solution, which will help take copper electroplating into the next decade and beyond. ATMI and Enthone's experience in impurities and their effects on film properties at higher levels is now informing the extension into 45nm and 32nm, improving stress migration, electro-migration, and the speed of bottom-up fill as deep geometries become more challenging.
ATMI and Enthone continue to expand their collaboration, particularly in moving the ViaForm plating solution beyond its current focus on materials alone. Working with major OEMs, ATMI and Enthone are exploring ways to integrate the ViaForm solution into the tools and equipment used in chip manufacture-yet another way in which ATMI's comprehensive knowledge of the semiconductor industry allows it to help that industry move forward with new and exciting technologies.
