Betting on liquid TSV processes for 3D integration
Meeting with eeNews Europe in Paris, Steve Lerner, Alchimer’s CEO made pretty bold statements about the state of the industry on 3D packaging and IC integration. When asked about the need for a new process flow or the limitations of current dry processes in use for the elaboration of through-silicon vias (TSVs), Lerner turned ironic “All the major players in the TVS industry are focusing on how to solve the problems inherent to directional deposition techniques such as physical vapour deposition (PVD), ionized PVD (iPVD), or chemical vapour deposition (CVD), just so they can keep selling their inadequate tools”.
“The tools that are used to build TSVs today were conceived for planar jobs”, he argues, “and they all fall apart when it comes to tackling 3D integration with complex, high-aspect ratio structures with recessed features”. One example Lerner likes to put forward is the emergence of tapered TSVs at conferences and seminars, heralded as the best fix to circumvent the poor fill factors and sidewall scalloping effects achieved with dry process flows. “Why turn to tapered vias when all what you want is to connect two layers with a minimal copper footprint?“ he questions, “That’s wasted real estate”. He remembers the days when Alchimer would present academic papers and concepts about the wet eG and cG technologies, enabling the deposition of highly-uniform isolation or barrier material layers for lining 3 micron diameter TSVs with true aspects ratios over 20:1 while maintaining an excellent step coverage.
“Nowadays, with about 200 patents filed or pending, we are confronting the Goliaths of the dry process industry with an unpleasant truth about the limitations of their solutions, and certain boards of conference no longer find our presence relevant. We are fighting our way against deeply entrenched companies and somehow, it is as if we were trying to sell an electric car to General Motors 20 years ago, they don’t want to see a new technology steal the show.” Lerner remarks. “We are also confronted with the Dilberts of this world”, lerner notes with humour, “for every one engineer of the wet culture, there are a thousand Dilbert engineers of the dry culture who won’t dare make a change for better, because we are still a fairly small company”.
Nowadays, 95% of Alchimer’s customers are located in Asia, and this is where Lerner sees the 3D integration happening first in high volume production, with China being a strong technology investor. Asian companies are not as much risk-averse as US companies, which explains Alchimer’s recent signing of a multi-level production collaboration agreement with South Korean chemical and equipment manufacturer KPM Tech that includes wet processing tools and materials for Alchimer’s through-silicon via platform. Alchimer also licensed its technology to a MEMS consortium in North America.
What differentiates Alchimer is its low-temperature wet approach, whereby mildly basic water-based chemistries are used to grow material layers directly on the silicon substrates or onto whatever chemically-compatible layer has been grown before, with strong chemical bonds. Each layer construction is reactant- and temperature-controlled for the chemicalgrafting process and reactant- and potential-controlled for the electrografting process, growing from the bottom up, hence forming a highly conformal layer regardless of the structure complexity, in the range of 50 to 300nm in thickness. The term “grafting” refers to the strong chemical bonds that form at the molecular level between the substrate and the film being grown. “Alchimer’s suite of AquiVia films covers the needs for isolation, barrier deposition and TSV copper fill at a less than half the cost offered by current dry processes while being compatible with existing wafer-processing infrastructures. ” explains Lerner, “what’s more, we don’t tie the hands of designers with primitive geometry rules” he adds.
Alchimer focuses on thin films because they are at a premium now, and this is where competition is, but Lerner also sees PCB manufacturers as the future market place since they can’t always afford the expensive dry process equipment needed for fine interposer geometries. Initially, Alchimer didn’t plan to get into the “copper fill” business, but then it realized it had the technology to fill copper vias in less than half the time required by competing processes, while drastically reducing the number of Chemical-Mechanical Polishing (CMP) steps that are usually needed to eliminate the excess of copper deposited with the typical successive dry processes.
The company recently joined the Global Semiconductor Association (GSA) and hopes to be able to push packaging and interposer design rules more aggressively thanks to its innovative solutions. “Some big guys have already designed 3D-integrated packages that can’t be done with dry processes” claims Lerner, “as soon as we can make some announcements and be taken more seriously, we’ll be able to talk to foundries and maybe EDA companies too. To hit the nail further, Alchimer has just announced a new wet deposition process called AquiVantage, that provides metallization for interposer and via-last in 3D packaging for chip-to-board interconnect. The process provides concurrent wet deposition of TSV and front-side isolation, barrier, and copper fill/interposer redistribution layers (RDLs), while eliminating CMP and dry deposition steps. On the backside, the AquiVantage process allows selective maskless growth of the on-silicon isolation layer, completely eliminating an entire expose/develop/etch/clean lithography process cycle.
Visit Alchimer at www.alchimer.com
Related news
Alchimer’s AquiVia TSV materials to be produced and distributed in Japan
Multi-level production collaboration between Alchimer and KPM Tech
Alchimer readies deposition process for TSV metallization
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