Tag Archives: process

ASM’s Haukka ALD Award

Dr. Suvi Haukka, executive scientist at ASM International, located in Finland, was awarded the ALD Innovation prize at the ALD 2016 Ireland conference (Figure), as chosen by the conference chairs. Haukka has had a lifetime career in Atomic Layer Deposition (ALD), starting at Microchemistry Ltd. with ALD pioneer Dr. Tuomo Suntola in 1990, and now holding over 100 patents.

Conference co-chairs Simon Elliott, Tyndall National Institute of Ireland (left) and Jonas Sundqvist, Lund University of Sweden (right) acknowledge Suvi Haukka from ASM International N.V. (center) as recipient of the “ALD Innovation Prize” at the 16th International Conference on Atomic Layer Deposition (ALD 2016) held last month in Dublin, Ireland. (Source: ALD 2016)

Since ASM bought Microchemistry in 1999, Haukka has worked on the manufacturability of ALD processes for the semiconductor industry. Today, ALD technology is essential for the high-volume manufacturing (HVM) of advanced ICs, with growing demand for the fabrication of nanoscale 3D devices such as finFETs and 3D-NAND Flash cells.

As reported by Riikka Puurunen in his ALD History Blog, Haukka joins a short list of technology luminaries who have been previous recipients of the prize:
* 2011 Roy Gordon (Harvard University),
* 2012 Markku Leskelä (University of Helsinki),
* 2013 Steven George (University of Colorado),
* 2014 Hyeongtag Jeon (Hanyang University), and
* 2015 Gregory Parsons (North Carolina State University).

More on the ALD 2016 conference can be read in the travel report blog.

[DISCLAIMER: Ed Korczynski and Jonas Sundqvist also work for TECHCET CA, and were co-chairs of the 2016 Critical Materials Conference.]

—E.K.

Eloquent Executives Ecosystem Expositions

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#cmc,#confab,#namedropping

With dimensional scaling reaching economic limits, each company in the IC fab industry must rely upon trusted connections with customers and suppliers to know which way to go, and the only way to gain trusted connections is through attending live events. Fortunately, whether you are an executive, and engineer, or an investor, there is at least one must-attend event happening these days to keep you informed.

We should always start with SEMI (sponsor of SemiMD, personal friends for many years) who has always represented the gold standard for trade-shows, executive events, and manufacturing symposia around the world. I attended my first SEMICON/West in 1988, and have since attended excellent SEMICONs in Europe, Japan, Korea, China, and Singapore. This year’s SEMICON gathering in San Francisco will feature a nearly 50% increase in the number of technical sessions.

SEMI ran another excellent Advanced Semiconductor Manufacturing Conference (ASMC) in Albany this month, featuring keynotes by visionaries such as “Nanoscale III-V CMOS” by MIT Professor Jesus A. del Alamo. The panel discussion “Moore’s Law Wall vs. Moore’s Wallet, and where do we grow from here,” was moderated by industry veteran Paul Werbaneth, now with Intevac. It is clear that we will reach economic limits of scaling well before the physical limits.

Materials technology and supply-chain solutions to extend economic limits were discussed by Intel’s VP of Technology and Manufacturing Tim Hendry in a keynote at the Critical Materials Conference (CMC) held this year in Oregon in early May, as produced by Techcet CA (I am also an analyst with Techcet and co-chair of this event, while Solid State Technology was a media sponsor). David Thompson, Senior Director, Center of Excellence in Chemistry, Applied Materials showed that despite the inherent “Agony in New Material Introductions – minimizing and correlating variabilities” is possible with improved collaboration throughout the supply-chain.

The Imec Technology Forum in Brussells this month (Solid State Technology was a media sponsor) could best be described with Lake Wobegone hyperbole that all the women were strong, the men were good-looking, and everyone was above average. The big news is imec acquiring iMinds for greater synergies when integrating the latter’s algorithms with imec-ecosystem hardware for application-specific solutions. Gary Patton, now CTO and SVP of Global R&D for GLOBALFOUNDRIES, reminded everyone at ITF of the inherent speed constraints of the copper wires and low-k dielectrics needed to connect IC transistors, “As I’ve often said, It’s like you have a Ferrari but you’re towing a boat if you don’t address the interconnect delay issues.” Regardless, Patton confidently declares that, “We will continue to provide value to our customers to be able to create new products, and we will innovate in ways other than simple scaling.”

At ITF, a video was shown of imec president Luc van den Hove interviewing Gordon Moore at his beachfront home in Hawaii. Moore has always been humble and claims no special ability to forecast trends. “It would not surprise me if we reached the end of scaling in the next decade,” said Moore. “I missed the importance of the PC, and I missed the importance of the internet. Predicting the future is a difficult job and I leave it to someone else.”

Wally Rhines seemed able to predict the future when he eloquent expounded upon Moore’s Law as a special-case learning-curve in his presentation at ITF. Rhines will provide one of the keynote addresses at the ConFab in Las Vegas this year (Solid State Technology’s home event, co-sponsored by SEMI and by IEEE-CPMT). Executives from the global industry will gather to hear insights and analysis on the challenges facing all companies in the ecosystem, as we search for profitable pathways in a more complex landscape.

—E.K.

SAQP Specs for 7nm finFETs

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As discussed in my last Ed’s Threads, lithography has become patterning as evidenced by first use of Self-Aligned Quadruple Patterning (SAQP) in High Volume Manufacturing (HVM) of memory chips. Meanwhile, industry R&D hub imec has been investigating use of SAQP for “7nm” and “5nm” node finFET HVM, as reported as SPIE-AL this year in Paper 9782-12.
The specifications for pitches ranging from 18 to 24 nanometers are as follow:

7.0nm Critical Dimension (CD) after etch,
0.5nm (3sigma) CD uniformity (CDU), and
<1nm Line-Width and Line-End Roughness (LWR and LER) assuming 10% of CD.

“Pitch walk”—variation in final pitch after multi-patterning—results in different line widths, and can result in subsequent excessive etch variation due to non-uniform loading effects. To keep the pitch walk in SAQP at acceptable levels for the 7nm node, the core-1 CDU has to be 0.5nm 3sigma and 0.8nm range after both litho and etch. In other presentations at SPIE-AL this year, the best LER after litho was ~4nm, improving to ~2nm after PEALD smoothing of sidewalls, but still double the desired spec.

The team at imec developed a SAQP flow using amorphous-Carbon (aC) and amorphous-Silicon (aSi) as the cores, and low-temperature Plasma-Enhanced Atomic-Layer Deposition (PEALD) of SiO2 for both sets of spacers. Bilayer DARC (SiOC) and BARC were used for reflectivity control. Compared to SAQP schemes where the mandrels are only aSi, imec claims that this approach saves 20% in cost due to the use of aC core and the elimination of etch-stopping-layers.

—E.K.

Litho becomes Patterning

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Once upon a time, lithographic (litho) processes were all that IC fabs needed to transfer the design-intent into silicon chips. Over the last 10-15 years, however, IC device structural features have continued to shrink below half the wavelength of the laser light used in litho tools, such that additional process steps are needed to form the desired features. Self-Aligned Double Patterning (SADP) schemes use precise coatings deposited as “spacers” on the sidewalls of mandrels made from developed photoresist or a sacrificial material at a given pitch, such that after selective mandrel etching the spacers pitch-split. SADP has been used in HVM IC fabs for many years now. Self-Aligned Quadruple Pattering (SAQP) has reportedly been deployed in a memory IC fab, too.

An excellent overview of the patterning complexities of SAQP was provided by Sophie Thibaut of TEL in a presentation at SPIE-AL on “SAQP integration using spacer on spacer pitch splitting at the resist level for sub-32nm pitch applications.” Use of a spacer-on-spacer process flow—enabled by clever combinations of SiO2 and TiO2 spacers deposited by Atomic Layer Deposition (ALD)—requires the following unit-process steps:
1 193i litho,
2 ALD spacers,
2 wet etches, and
4 plasma etches.

Since non-litho processes dominate the transfer of design-intent to silicon, from first principles we should consider such integrated flows as “patterning.” Etch selectivity to remove one material while leaving another, and deposition dependent on underlying materials determine much of the pattern fidelity. Such process flows are new to IC fabs, but have been used for decades in the manufacturing of Micro-Electrical Mechanical Systems (MEMS), though generally on a patterning length scale of microns instead of the nanometers needed for advanced ICs. R&D labs today are even experimenting with Self-Aligned Octuple Patterning (SAOP), and based on the legacy of MEMS processing it certainly could be done.

—E.K.

ALD of Crystalline High-K SHTO on Ge

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Alternative channel materials (ACM) such as germanium (Ge) will need to be integrated into future CMOS ICs, and one part of the integration was shown at the recent Materials Research Society (MRS) spring meeting by John Ekerdt, Associate Dean for Research in Chemical Engineering at the University of Texas at Austin, in his presentation on “Atomic Layer Deposition of Crystalline SrHfxTi1-xO3 Directly on Ge (001) for High-K Dielectric Applications.”

Strontium hafnate, SrHfO3 (SHO), and strontium titanate, SrTiO3 (STO), with dielectric constants of ~15 and ~90 (respectively) can be grown directly on Ge using atomic layer deposition (ALD). Following a post-deposition anneal at 550-590°C for 5 minutes, the perovskite films become crystalline with epitaxial registry to the underlying Ge (001) substrate. Capacitor structures using the crystalline STO dielectric show a k~90 but also high leakage current. In efforts to optimize electrical performance including leakage current and dielectric constant, crystalline SrHfxTi1-xO3 (SHTO) can be grown directly on Ge by ALD. SHTO benefits from a reduced leakage current over STO and a higher k value than SHO. By minimizing the epitaxial strain and maintaining an abrupt interface, the SHTO films are expected to reduce dielectric interface-traps (Dit) at the oxide-Ge interface.

Much of the recent conference has been archived, and can now be accessed online.

—E.K.

CMP Slurry Trade-offs in R&D

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As covered at SemiMD.com, the CMP Users Group (of the Northern California Chapter of The American Vacuum Society) recently held a meeting in Albany, New York in collaboration with CNSE, SUNY Polytechnic Institute, and SEMATECH. Among the presentations were deep dives into the inherent challenges of CMP slurry R&D.
Daniel Dickmann of Ferro Corporation discussed trade-offs in designing CMP slurries in his presentation, “Advances in Ceria Slurries to Address Challenges in Fabricating Next Generation Devices.” Adding H2O2 to ceria slurry dramatically alters the zeta-potential of the particles and thereby alters the removal rates and selectivities. For CMP of Shallow Trench Isolation (STI) structures, adding H2O2 to the slurry allows for lowering of the particle concentration from 4% to <2% while maintaining the same removal rate. Reducing the average ceria particle size from 130nm to 70nm results in a reduction in scratch defects while maintaining the same removal rate by tuning the chemistry, but the company has not yet found chemistries that allow for reasonable removal rates with 40nm diameter particles. The ceria morphology is another variable that must be controlled according to Dickmann, “It can seem counter-intuitive, but we’ve seen that non-spherical particles can demonstrate superior removal-rates and defectivities compared to more perfect spheres.”
Selectivity is one of the most critical and difficult aspects of the CMP process, and arguably the key distinction between CMP and mere polishing. The more similarity between the two or more exposed materials, the more difficult to design high selectivity in a slurry. Generally, dielectric:dielectric selectivity is difficult, and how to develop a slurry that is highly selective to nitride (Si3N4) instead of TEOS-oxide (PECVD SiO2 using tetra-ethyl-ortho-silicate precursor) was discussed by Takeda-san of Fujimi Corporation. In general, dielectric CMP is dominated by mechanical forces, so the slurry chemistry must be tuned to achieve selectivity. Choosing <5 pH for the slurry allows for reducing the oxide removal rate while maintaining the rate of nitride removal. Legacy nitride slurries have acceptable selectivities but unacceptable edge-over-erosion (EOE) – the localized over-planarization often seen near pattern edges. Reducing the particle size reduces the mechanical force across the surface such that chemical forces dominate the removal even more, while EOE can be reduced because negatively charged particles are attracted to the positively charged nitride surface resulting in local accumulation.
—E.K.