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ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 19 NO. 2
CHARACTERIZING ORGANIC NANOCONTAMINATION
IN SEMICONDUCTORS BY RESONANCE-ENHANCED
NANOSCALE IR SPECTROSCOPY (AFM-IR)
Anirban Roy and Jay Anderson
Anasys Instruments Corp.
EDFAAO (2017) 2:31-34 1537-0755/$19.00 ©ASM International®
INTRODUCTION
For the last few decades, continuous development in
semiconductor process technology has led to the fabrica-
tion of deviceswith nanometer-scale features.[1] Growth in
the nanotechnology techniques used inproducingmicro-/
nano-electromechanical components results in a growing
interest for nanoscale surface analysis techniques that
can complement or may replace the currently available
tools. Resonance-enhanced AFM-IR is an emerging tech-
nique with the potential to overcome some limitations of
the existing tools used in semiconductor fabs and failure
analysis labs.
Organic contaminants are one of the major sources
of surface contamination in the process development
steps. Typical organic contaminants in the semiconductor
fabrication facility include residual photoresists, human
skin flakes, hair, and fabric from clothes and/or personal
protective equipment such as gloves, lab coats, masks,
and so on. Characterizing nanoscale organic contamina-
tion poses a major challenge to the traditional failure
analysis technique, as discussed below.
BACKGROUND
Scanning electron microscopy coupled with energy-
dispersive x-ray spectroscopy, one of the industry stan-
dards in surface analysis with nanometer-scale spatial
resolution, offers useful chemical insight into surface
defects and contamination; however, it providesminimal
information for organic components. Among other alter-
native analytical techniques, infrared (IR) spectromi-
croscopy provides superior results in identifying organic
materials but lacks spatial resolution. The traditional
mid-IR spectromicroscopic defect analysismethods offer
diffraction-limited detection resolution only up to 3 to
10 µm or larger.[2] Raman spectroscopy, on the other
hand, provides similar chemical insight with submicrom-
eter spatial resolution due to the short excitation wave-
lengths.[3] Nevertheless, the application of traditional
Raman spectromicroscopy in nanoscale defect analysis is
still limited due to experimental factors such as excitation
wavelength, depth of penetration, and the transparency
of microelectronic circuits.
Atomic force microscopy (AFM), a well-known scan-
ning probe imaging technique, yields high-spatial-
resolution topographic maps of a sample surface. Many
surface-imaging techniques based on AFM also provide
image contrast from material characteristics such as
surface mechanical, electrical, and magnetic properties.
While these properties can be mapped with high spatial
resolution and can provide critical insight into the surface
defects, none of these methods provide robust chemical
analysis, especially for unknown materials. However,
when a traditional AFM is combinedwith IR spectroscopy,
the resulting AFM-IR technique provides high-resolution
topographic maps with the addition of nanoscale chemi-
cal imaging and spectroscopy.
Previously, King et al. reported the applications of
AFM-IR technology innanoscale chemical andmechanical
“WHEN THE TRADITIONAL AFM IS
COMBINED WITH IR SPECTROSCOPY,
THE RESULTING AFM-IR TECHNIQUE
PROVIDES HIGH-RESOLUTION
TOPOGRAPHIC MAPS WITH THE
ADDITION OF NANOSCALE CHEMICAL
IMAGING AND SPECTROSCOPY.”