From The National Institute of Standards and Technology: “No Fib:: NIST Unmasks a Superfast Process for Nanoscale Machining”

From The National Institute of Standards and Technology

8.23.22
Technical Contacts

Samuel M. Stavis
samuel.stavis@nist.gov
(301) 975-2844

Andrew Madison
andrew.madison@nist.gov
(301) 975-5265

1
NIST researchers have demonstrated that a focused ion beam (FIB) can fabricate microscopic devices with fine resolution and without sacrificing high speed. Left: The conventional FIB process requires a narrow, low-current ion beam to fabricate a miniature version of a lighthouse lens in silica glass with fine resolution. Because the beam has a low current of ions, the method is time consuming. Right: Placing a protective layer of chromium oxide over the silica glass enables machinists to use a much higher-current ion beam, allowing them to fabricate the same lenses 75 times faster. Credit: Andrew C. Madison/Samuel M. Stavis/NIST.

Cutting intricate patterns as small as several billionths of a meter deep and wide, the focused ion beam (FIB) is an essential tool for deconstructing and imaging tiny industrial parts to ensure they were fabricated correctly. When a beam of ions, typically of the heavy metal gallium, bombards the material to be machined, the ions eject atoms from the surface—a process known as milling—to sculpt the workpiece.

Beyond its traditional uses in the semiconductor industry, the FIB has also become a critical tool for fabricating prototypes of complex three-dimensional devices, ranging from lenses that focus light to conduits that channel fluid. Researchers also use the FIB to dissect biological and material samples to image their internal structure.

However, the FIB process has been limited by a trade-off between high speed and fine resolution. On the one hand, increasing the ion current allows a FIB to cut into the workpiece deeper and faster. On the other hand, the increased current carries a larger number of positively charged ions, which electrically repel each other and defocus the beam. A larger, diffuse beam, which can be about 100 nanometers in diameter or 10 times wider than a typical narrow beam, not only limits the ability to fabricate fine patterns but can also damage the workpiece at the perimeter of the milled region. As a result, the FIB has not been the process of choice for those trying to machine many tiny parts in a hurry.

Now researchers at the National Institute of Standards and Technology (NIST) have discovered that a masking process can virtually eliminate this trade-off, enabling a FIB to machine at high current (and therefore high speed) without sacrificing fine resolution. The finding could dramatically expand the utility of FIBs, not only for researchers fabricating prototypes and preparing samples, but also for manufacturers in the semiconductor industry who need rapid analysis, repair, or customization of structures and devices.

“In both research and in production, the need for speed is real,” said NIST researcher Andrew C. Madison.

Madison and his colleagues at NIST, including Samuel M. Stavis and a collaborator from the University of Maryland NanoCenter in College Park, compared the efficiency of two processes for achieving fine resolution with a FIB. In one process, fabricators simply use a FIB with a low-current, narrow beam to slowly but carefully sculpt the workpiece—similar to the way a painter with a fine brush painstakingly creates sharp details.

The other method employs a higher-current, wider beam along with a mask, or thin film, deposited on the workpiece. The central, most intense region of the ion beam penetrates the mask and blasts the underlying material to form the pattern. The outer, less intense region of the beam is blocked by the mask, protecting the sample from damage at the edges of the pattern.

The masking process is similar to that of a painter who puts masking tape around the edges of a wide area and then uses a roller rather than a fine brush to rapidly paint the wide area while still achieving sharp edges.

The NIST team determined that beams of much higher-than-normal current can be used without compromising the fine details of the pattern. Previous studies examining masking focused only on improving resolution without considering the effect of the mask on the speed of fabrication. Whereas the finer resolution provided by the masking process was plainly evident from these studies, the NIST researchers discovered a much greater improvement in speed.

The researchers used chromium oxide as a mask, studying its material properties and how gallium ions from the FIB interacted with it. They then employed a high-current, wide beam to blast a checkerboard test pattern into silica glass. They found that the masking process not only provided similarly fine resolution to the unmasked, narrow-beam process, but also milled the sample much faster due to the higher beam current.

Encouraged by the result, the team then used the mask with a wide, high-current beam to machine compact Fresnel lenses—microscopic versions of lighthouse lenses—which are useful in optical devices ranging from solar cells to atom traps. Even though the high-current beam was about 10 times wider than the low-current beam, the method yielded lenses that performed the same to within an uncertainty of 1%. In this way, the researchers confirmed that they could fabricate similar lenses 75 times faster than they could using the conventional process. “If time is money, then our process enables a big sale on small lenses—75 for the price of one,” said Stavis. “Want to mill fast? Get you a mask,” he added. The team reported their findings in Advanced Functional Materials on August 21, 2022.

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

NIST Campus, Gaitherberg, MD.

The National Institute of Standards and Technology’s Mission, Vision, Core Competencies, and Core Values

Mission

To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

NIST’s vision

NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.

NIST’s core competencies

Measurement science
Rigorous traceability
Development and use of standards

NIST’s core values

NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
Integrity: We are ethical, honest, independent, and provide an objective perspective.
Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

Background

The Articles of Confederation, ratified by the colonies in 1781, contained the clause, “The United States in Congress assembled shall also have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States”. Article 1, section 8, of the Constitution of the United States (1789), transferred this power to Congress; “The Congress shall have power…To coin money, regulate the value thereof, and of foreign coin, and fix the standard of weights and measures”.

In January 1790, President George Washington, in his first annual message to Congress stated that, “Uniformity in the currency, weights, and measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to”, and ordered Secretary of State Thomas Jefferson to prepare a plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States, afterwards referred to as the Jefferson report. On October 25, 1791, Washington appealed a third time to Congress, “A uniformity of the weights and measures of the country is among the important objects submitted to you by the Constitution and if it can be derived from a standard at once invariable and universal, must be no less honorable to the public council than conducive to the public convenience”, but it was not until 1838, that a uniform set of standards was worked out. In 1821, John Quincy Adams had declared “Weights and measures may be ranked among the necessities of life to every individual of human society”.

From 1830 until 1901, the role of overseeing weights and measures was carried out by the Office of Standard Weights and Measures, which was part of the U.S. Coast and Geodetic Survey in the Department of the Treasury.

Bureau of Standards

In 1901 in response to a bill proposed by Congressman James H. Southard (R- Ohio) the National Bureau of Standards was founded with the mandate to provide standard weights and measures and to serve as the national physical laboratory for the United States. (Southard had previously sponsored a bill for metric conversion of the United States.)

President Theodore Roosevelt appointed Samuel W. Stratton as the first director. The budget for the first year of operation was $40,000. The Bureau took custody of the copies of the kilogram and meter bars that were the standards for US measures, and set up a program to provide metrology services for United States scientific and commercial users. A laboratory site was constructed in Washington DC and instruments were acquired from the national physical laboratories of Europe. In addition to weights and measures the Bureau developed instruments for electrical units and for measurement of light. In 1905 a meeting was called that would be the first National Conference on Weights and Measures.

Initially conceived as purely a metrology agency the Bureau of Standards was directed by Herbert Hoover to set up divisions to develop commercial standards for materials and products. Some of these standards were for products intended for government use; but product standards also affected private-sector consumption. Quality standards were developed for products including some types of clothing; automobile brake systems and headlamps; antifreeze; and electrical safety. During World War I, the Bureau worked on multiple problems related to war production even operating its own facility to produce optical glass when European supplies were cut off. Between the wars Harry Diamond of the Bureau developed a blind approach radio aircraft landing system. During World War II military research and development was carried out including development of radio propagation forecast methods; the proximity fuse and the standardized airframe used originally for Project Pigeon; and shortly afterwards the autonomously radar-guided Bat anti-ship guided bomb and the Kingfisher family of torpedo-carrying missiles.

In 1948, financed by the United States Air Force the Bureau began design and construction of SEAC: the Standards Eastern Automatic Computer.


The computer went into operation in May 1950 using a combination of vacuum tubes and solid-state diode logic. About the same time the Standards Western Automatic Computer, was built at the Los Angeles office of the NBS by Harry Huskey and used for research there. A mobile version- DYSEAC- was built for the Signal Corps in 1954.

Due to a changing mission, the “National Bureau of Standards” became the “National Institute of Standards and Technology” in 1988.

Following September 11, 2001, NIST conducted the official investigation into the collapse of the World Trade Center buildings.

Organization

NIST is headquartered in Gaithersburg, Maryland, and operates a facility in Boulder, Colorado, which was dedicated by President Eisenhower in 1954. NIST’s activities are organized into laboratory programs and extramural programs. Effective October 1, 2010, NIST was realigned by reducing the number of NIST laboratory units from ten to six. NIST Laboratories include:

Communications Technology Laboratory (CTL)
Engineering Laboratory (EL)
Information Technology Laboratory (ITL)
Center for Neutron Research (NCNR)
Material Measurement Laboratory (MML)
Physical Measurement Laboratory (PML)

Extramural programs include:

Hollings Manufacturing Extension Partnership (MEP), a nationwide network of centers to assist small and mid-sized manufacturers to create and retain jobs, improve efficiencies, and minimize waste through process improvements and to increase market penetration with innovation and growth strategies;
Technology Innovation Program (TIP), a grant program where NIST and industry partners cost share the early-stage development of innovative but high-risk technologies;
Baldrige Performance Excellence Program, which administers the Malcolm Baldrige National Quality Award, the nation’s highest award for performance and business excellence.

NIST’s Boulder laboratories are best known for NIST‑F1 which houses an atomic clock. NIST‑F1 serves as the source of the nation’s official time. From its measurement of the natural resonance frequency of cesium—which defines the second—NIST broadcasts time signals via longwave radio station WWVB near Fort Collins in Colorado, and shortwave radio stations WWV and WWVH, located near Fort Collins and Kekaha in Hawai’i, respectively.

NIST also operates a neutron science user facility: the NIST Center for Neutron Research (NCNR).

The NCNR provides scientists access to a variety of neutron scattering instruments which they use in many research fields (materials science; fuel cells; biotechnology etc.).

The SURF III Synchrotron Ultraviolet Radiation Facility is a source of synchrotron radiation in continuous operation since 1961.

SURF III now serves as the US national standard for source-based radiometry throughout the generalized optical spectrum. All NASA-borne extreme-ultraviolet observation instruments have been calibrated at SURF since the 1970s, and SURF is used for measurement and characterization of systems for extreme ultraviolet lithography.

The Center for Nanoscale Science and Technology performs research in nanotechnology, both through internal research efforts and by running a user-accessible cleanroom nanomanufacturing facility.

This “NanoFab” is equipped with tools for lithographic patterning and imaging (e.g., electron microscopes and atomic force microscopes).

Committees

NIST has seven standing committees:

Technical Guidelines Development Committee (TGDC)
Advisory Committee on Earthquake Hazards Reduction (ACEHR)
National Construction Safety Team Advisory Committee (NCST Advisory Committee)
Information Security and Privacy Advisory Board (ISPAB)
Visiting Committee on Advanced Technology (VCAT)
Board of Overseers for the Malcolm Baldrige National Quality Award (MBNQA Board of Overseers)
Manufacturing Extension Partnership National Advisory Board (MEPNAB)

Measurements and standards

As part of its mission, NIST supplies industry, academia, government, and other users with over 1,300 Standard Reference Materials (SRMs). These artifacts are certified as having specific characteristics or component content, used as calibration standards for measuring equipment and procedures, quality control benchmarks for industrial processes, and experimental control samples.

Handbook 44

NIST publishes the Handbook 44 each year after the annual meeting of the National Conference on Weights and Measures (NCWM). Each edition is developed through cooperation of the Committee on Specifications and Tolerances of the NCWM and the Weights and Measures Division (WMD) of the NIST. The purpose of the book is a partial fulfillment of the statutory responsibility for “cooperation with the states in securing uniformity of weights and measures laws and methods of inspection”.

NIST has been publishing various forms of what is now the Handbook 44 since 1918 and began publication under the current name in 1949. The 2010 edition conforms to the concept of the primary use of the SI (metric) measurements recommended by the Omnibus Foreign Trade and Competitiveness Act of 1988.