Sunday Session, June 24th, 2018
John Nibarger, NIST, Boulder
Audience participated in a discussion of cleanroom utilities, especially water and gases.
A basic description was provided on how cleanrooms require many air changes and a lot of water for cooling and high quality for processing.
– NIST at Boulder added nitrogen generators. This cut their nitrogen costs in half and the investment broke even at 18 months. However, this does not include power to run N2 generators.
– Purity from evaporative nitrogen is typically five nines.
– To get five nines purity from nitrogen generators is quite slow.
– What if there’s a power loss? Automatically switches to LN2.
– If thinking of switching to nitrogen generators, consider whether vendor owns your existing LN2 tank, and also what your contract with the supplier stipulates.
If considering cutting costs of nitrogen, take a look at the NIST-Gaitherburg survey of LN2 use. Many are using nitrogen for air tables rather than CDA.
– Advice: adding meter to charge for nitrogen, users will switch to CDA.
Considering generators for H2?
– Quite reasonable to use H2 generators, especially considering the lead time for bottles.
– Recommend one bottle for backup.
– The gas generators do need to be maintained and should have a maintenance contract, especially regarding controls issues
– need DI water
– Will generate O2, but needs to be dried.
– Also consider the cost of highly skilled workers changing bottles.
Also considered: Airshowers
– To be effective, users must also follow other rules too, or the shower will be ineffective.
– easy to clean by staff
– 10minutes to wash
– Consider the art of pulling up regular mats. Done improperly sends particles everywhere.
Gloves and wipes, Greg Heiland, Valutek
Discussion involved especially proper purchasing of glove and wipes for the cleanroom.
Gloves should be stored with cuffs to front to avoid contamination from skin.
They should have no pigments that may serve as contaminants.
Proper cleanroom gloves should have post-processing washes and testing.
Question: Which gloves are best for which applications?
– PVC gloves ok if not used for wet chemistry.
– Latex is good for handling tools.
– Nitrile is best for cleanrooms, static dissipative.
Question: Is there an allergic reaction to nitrile:
– That would be very unusual. More likely it is an allergic reaction to contaminants on hands prior to donning gloves.
Should gloves be put on prior to gowning?
– Best is two gloves, one for donning and touching garment, then donning cleanroom gloves after gowning.
– Defined by substrates, edge treatment.
– Ultrasonic is best edge treatment.
– Use dry for spills
– Using wet, want 38% saturated, remaining 62% for contaminants, particles (although there is no practical way to measure 38% saturation).
– 70% of contaminants come from operator behavior.
Nanolab Management, Matt Moneck, CMU
There was a broad discussion of
– Surveys provide basis for proper staffing levels. Reference of those surveys provided the CMU nanofab sufficient justification for increasing staffing.
– Service contracts are cost prohibitive, there is a average of 3 per facility
– This depends upon who owns the system.
– It’s worth negotiating with the department or university to help support systems that they had advocated for.
– When writing the Request for Proposal, build in training, extended warrantees up front
– buy service contracts upfront, free phone support
– Few facilities have training videos but they all want them.
– Social media such as Slack and WhatsApp can be useful for helping users who have realtime issues with tools. They can also mitigate wrong information that is propagated through the user community.
– Users don’t care because they don’t report to nanofab staff.
– need buy-in from faculty.
– Some user infractions are not callous disregard but rather are caused by poor training
Making them write a 10 page report on why what they did was dangerous can be a strong deterrent.
– Vidoe is useful: when users see themselves doing bad things in a video is very effective in remedying the behavior.
– Also, a monitor viewable in public can also serve as a deterrent to bad behavior.
– Users should be given safety and lab protocol refresher:
– Either an annual refresher…
– … or a quarterly refresher for 25% of the users. A smaller group promotes more involvement and questions.
– Soft caps and notched cap are alternatives to hard caps and no cap.
– Soft caps reduces the rate above a certain total.
-Notched caps provide a cap that terminates at a certain total.
Nanolab IT, Dylan Klomparens, NIST-Gaithersburg
Discussion was around cleanroom controls, scheduling and access via IT systems.
Here are some key points during the presentation:
Cloud infrastructure provides better reliability.
Wireless is great but too many devices can cause interference.
Cost to add new wired Ethernet jack ~$1500.
Managing user accounts through Facebook or Google leaves password management to them, especially two-factor authentication.
SneakerNet is a virus issue. NIST limits flash drives to only two access points in lobby since they are a significant vector for viruses.
Good idea to add graphic to desktop indicating that personal data should not be kept on that computer, especially to protect facility from issues with external users.
Some apps that can help with managing users:
– Experitest is a German software for storing process data.
– Amazon Glacier very inexpensive for backup.
– Discourse used for user forum.
Monday Session, June 25th, 2018
Jered Haun, PhD, UC Irvine
Dr Haun’s goal in the end is a point-of-care device that will accept a ~1cm tumor tissue biopsy and output single cell samples for analysis. This was developed stepwise using:
- tissue digestion and filtration device
- microfluidic channels that generate high-shear flows to disaggregate cell aggregates
Fabrication was by CO2 laser tools to fabricate acrylic features that were then assembled in layers.
The results dramatically improved the count of single cells over standard collagenase procedures.
Defining the Grey Area: Materials and Control, Ryan Rivers, UC Berkeley
Ryan described an elegant graphic to define the contamination risk of a substrate that consists of four color keys that define the types of contamination:
These are arranged per the attached image, with a severity defined from 0-4.
This provides a go/ no go criteria for each tool in the cleanroom. The payoff is less time spent providing this same information in an ad hoc approach.
The question was posed regarding the graduate student who desperately needs to get their work done. In response, this approach actually clears up enough time to deal with those rarer situations that demand a more nuanced decision.
Energy Efficient Cleanroom Design, Greg Owen, GLO Consulting
Cleanrooms operate by exchanging air through ultrafiltration units.
Air management systems consume 27% of cleanroom utility costs.
Plenum deliver is most efficient.
Costs can be decreased by increasing filter areas.
Fan motor rpm has a strong effect on efficiency and noise.
A question was asked about the CFM in the gowning room, should it be lower than process areas. Yes, that is typical.
Vibration Control, Steven Ryan, TMC
For cleanroom and characterization purposes, low frequency vibrations (~10Hz) are controlled. Traditionally a concrete plinth with spring and damper has been used, but this is not sufficient for imaging the smallest features on the order of Angstroms. This requires active feedback. A massy plinth would need a big motor. A better approach is to measure the floor movement and cancel that motion before it reaches the mass.
It is possible to use two-stage isolation if measures are taken to avoid instability.
It should be considered that vibration levels rise over time as the building is populated with more people and equipment.
The question was asked confirming that more than 1 axis of vibration was being controlled. The answer was that 6 degrees of freedom are controlled, including yaw, roll, and pitch.
Lloyd Whitman, White House, Office of Science and Technology Policy
The Office of Science and Technology Policy provides advice to white house, which in turn sets R&D priorities. Among those priorities are to lead in research and technology, including nanofabrication. Other priorities are high-performance computing, increase in technology transfer, AI, and autonomous systems. The idea is to promote these technologies without over-regulating them.
It was noted that the R&D budget ($177B) has increased over 10% for 2018 and 2019. However, caps return in 2020 unless Congress makes changes.
A large portion of the budget goes to DARPA programs due to concerns about security and reliability of the nation’s defense.
One question was about the prioritization of STEM education. The response was that the federal government does not have much power to set education priorities because education is not a federated system. Changing the education system is done most effectively through local school boards.
Dr Whitman emphasized after the question period that AI may make major changes to the scientific method. Consider how Google Maps now provides routes based on existing traffic. AI may make it possible to mine scientific literature and produce a research approach. This may shorten the path to PhD degrees and possibly democratize research.
Lithography Use over 15 Years, Jörg Scholvin, MIT
Data was mined from Coral over 15 of lithography use.
Two major trends:
- Wafer lots decreased
- Maskless writing increased
Question: who uses maskless?
Those who had established processes tended to stick with contact lithography rather than develop a new process for direct write. New users tended to go directly to maskless.
Tuesday Session, June 26th, 2018
EBL Systems and Methods, Don Tennant, Cornell
Resolution vs throughput follows a power law. If the beam is moving, it’s the equivalent of a bigger beam spot size.
Gain error is due to z location. This can be exploited to make small changes in pitch.
It is important to have global and local alignment marks because wafer warps during processing.
100kV is good for most applications.
Autofocus works much better now than it used to.
Be careful of aliasing on curved features.
Question: is EBL getting faster. The electronics limits the speed.
The question was asked about etch selectivity with EBL exposures. The answer was that we can assume exposed areas have same chemical properties. Except HSQ.
Precise Invoicing of Resist, Leif Johansen, Danish Technical University
This is enabled by automated spin coaters that draw resist from a weighed canister. The scale has a digital output to a logging system.
They can also monitor the waste bottle level.
This can be applied to PVD systems by monitoring the crystal output.
The question was asked about the cost recover. They recover about 90% of the resist cost. The 10% is due to other coating methods that cannot be monitored, such as those dispensed by pipet, especially on small substrates. SU8 is not monitored yet.
General discussion of Cleanroom Safety
Several speakers discussed lab safety, especially regarding lab buddies.
At the Lurie Nanofabrication Facility at University of Michigan, after hours users are required to wear a nametag that is legible with the surveillance cameras.
Work-study students are during after hours as safety buddies.
At MIT, users who are approved to work after hours are issued a buddy card. This they exchange with their buddy when they work after hours. They must check in with their safety buddy hourly via email.
The safety buddy can be remote (in an adjacent building) except in the case of hazardous chemicals use, in which the case the buddy must be in the lab.
The user must submit the email chain after they finish in the lab to prove that they followed the safety protocol.
It was noted that users only encouraged being a user’s safety buddy if they have confidence in that user’s safety hygiene.
In India, drills are also held in the evening to broaden the training.
By the panic button, they have a “What needs to be done” sheet.
Users undergo reorientation every 6 months, and are tested yearly.
They have coordinated with the local hospital for HF exposure. Only ambulances from that hospital are called for emergencies.
Wednesday Session, June 27th, 2018
Vacuum Pump Maintenance, Ed Ho, Pfeiffer Vacuum
Ed polled the audience on pump maintenance. The comment was made, half-joking, that we just run them to failure. In all seriousness, the definition of failure is important. A pump on an SEM may be in failure due to vibrations being above the tool threshold, but still be fine for a PVD. Also, run to failure for a rotary vane pump is far less expensive than running a turbo pump to failure.
Pfeiffer’s goal is to have a green, yellow, and red LED pump health indicator on their pumps. This is not yet available, but they can get data off some pumps to analyze health and inform when a PM is called for.
It was noted, regarding turbo pumps, that buildup of tool effluent on the blades is highest when the pump is not rotating, especially because pumps tend to be the coolest component in the exhaust. Heating the pump is not recommended.
Pump life can be extended by linking the roughing and turbo pump so that speed can be reduced after reaching vacuum pressure.
Maglev has been more expensive than bearing pumps, but they are becoming more competitively priced.
RFID interlocks, Tom Ferraguto, UMass, Lowell
Tom is implementing RFID devices for interlocking tools.
They currently operate on the honor system for actual tool use, but video reconciliation showed 14% more actual tool time than was reported by users.
He first tried Easy Clocking, which is a time clock RFID device. This turned out to not be robust enough, specifically the touchpad did not hold up, and the programming was difficult.
Keytroller is a wireless industrial RFID device used for enabling forklifts, etc. It can be powered directly of with batteries. The price is about $1400 wireless. It is currently being tested.
A question was asked about possible interference from other RFID devices, but that cannot be currently determined as he is only testing a small number of devices.
A comment was made about network outages. Local collection is uploads data at regular intervals can resolve that issue.
Demonstration of the NEMO system developed at NIST, Dylan Klomparens, NIST
NEMO was developed in-house at NIST to replace Coral. Dylan demonstrated this.
Anyone can try out NEMO with sample data. Go to this Readme document to learn how:
NIST also uses wall-mounted Windows Surface tablets for login and logout of the cleanroom. They use PcProx Plus RFID readers and users really like them.
Nemo has affected behavior by monitoring reservation behavior, scoring users on how frequently they change or cancel reservations. This has prompted more careful planning by the users.
The question was asked whether others can contribute? They are working on making NEMO more modular to make it easier to add features. Dylan felt obligated to point out that he works for NIST and is not in a position to develop features in NEMO for other fabs.
It was asked whether tool data, or at least tool specs can be transferred into NEMO. I can do bulk imports of data.
Workforce Development, David Gottfried (Georgia Tech) and Jessie Zhang (NIST)
Nanofab users may have process experience, but have none on tool maintenance.
NIST Gaithersburg has had a program with Hudson Valley Community College that has been successful. It started out as 12 weeks but was extended to 16 weeks to accommodate the extensive initial safety and tool training.
The students need repetitive practice on tools, but not too many tools.
One clear advantage these students have in job interviews is the ability to speak the language of industry, such as contamination, pumps and vacuum systems, as well as SPC.
The question was asked about who funds the program.
Intially, NSF kicked in 50% though now NIST pays 100%. But Hudson Valley CC pays stipend and arranges housing, which relieves a significant logistical burden and NIST only has to deal with the training program itself. Schools cover insurance.
For anyone looking to initiate a program like this, there are NSF program managers who would like to have this type of program in their portfolio.
What are their salaries? ~55k.