Using
a novel prototyping method, two materials scientists at NIST are
creating "libraries" of inorganic thin films that may make it
easier for chipmakers to find new films for next-generation ICs.
The
method, called pulsed laser deposition (PLD), uses a chamber containing
a dual-target assembly that rotates to make the entire target
surface available during deposition. The method enables the researchers
to vary the thickness and chemical composition of the films, according
to NIST. Volume production of film samples with two or more compounds
should facilitate the search for new materials.
The
compounds are called "library films" because their properties
can vary substantially in small areas, which makes them suitable
for high-throughput analysis using tools such as SEM, TEM, and
AFM. To demonstrate the technique, scientists Peter Schenck (inset)
and Debra Kaiser in the ceramic division's PLD facility have created
libraries of barium strontium titanate (BST) films. They note
that BST films are a potential replacement for SiO2
insulators in advanced DRAMs. The double-beam system (left) splits
a 248-nm excimer laser beam in order to strike two separate starting
materials at the same time. When the target materials vaporize
they create gas plumes such as the one in the large image shown
above. The plumes mix before depositing on a silicon wafer inside
a multiport chamber with an oil-free vacuum pump.
Schenck
and Kaiser control both the composition and thickness of the deposited
film. They've used their technique to make samples with narrow
bands of uniform thickness while systematically varying the amounts
of barium, strontium, and titanium across each band. The series
of falsecolor intensity-coded images above shows an expanding
laser-generated plume from a barium titanate target. From a sideways
view of the target, the field of view measures approximately 1
x1 cm.
The sequence lasted 600 nanoseconds. Other films the pair has
produced include lead zirconate titanate, alumina, zirconia, and
silver/magnetite nanocomposites.
The
compounds are called "library films" because their properties
can vary substantially in small areas, which makes them suitable
for high-throughput analysis using tools such as SEM, TEM, and
AFM. To demonstrate the technique, scientists Peter Schenck (inset)
and Debra Kaiser in the ceramic division's PLD facility have created
libraries of barium strontium titanate (BST) films. They note
that BST films are a potential replacement for SiO2
insulators in advanced DRAMs. The double-beam system (left) splits
a 248-nm excimer laser beam in order to strike two separate starting
materials at the same time. When the target materials vaporize
they create gas plumes such as the one in the large image shown
above. The plumes mix before depositing on a silicon wafer inside
a multiport chamber with an oil-free vacuum pump. 
