In this paper, we present our most recent approach on the extraction of reliable atomic force microscopy (AFM) tip dimensions from scanning electron microscopy (SEM) images in order to answer future requirements on ever shrinking CD AFM tips. We demonstrate the capabilities of a newly developed, fully automatic analysis software based on advanced SEM image modeling and user a-priori knowledge integration in SEM image analysis algorithm. The impact of such breakthrough technology will be shown as a function of its stability and robustness by varying tip shape, imaging settings, and SEM setup parameters. The extracted values are compared to data yielded from a commonly used SEM image analysis approach based on threshold type algorithms, and directly related to reference CD AFM measurements. We will discuss the prospective challenges accompanied with shrinking tip dimensions and the potential of a comprehensive data fusion approach, which can be used for both R&D and high volume production.
The controlled deposition of materials by means of electron beam induced processing (EBIP) is a well-established
patterning method, which allows for the fabrication of nanostructures with high spatial resolution in a highly precise and
flexible manner. Applications range from the production of ultrathin coatings and nanoscaled conductivity probes to
super sharp atomic force microscopy (AFM) tips, to name but a few. The latter are typically deposited at the very end of
silicon or silicon-nitride tips, which are fabricated with MEMS technologies. EBIP therefore provides the unique ability
to converge MEMS to NEMS in a highly controllable way, and thus represents an encouraging opportunity to refine or
even develop further MEMS-based features with advanced functionality and applicability.
In this paper, we will present and discuss exemplary application solutions, where we successfully applied EBIP to
overcome dimensional and/or functional limitations. We therefore show the fabrication stability and accuracy of “T-like-shaped”
AFM tips made from high density, diamond-like carbon (HDC/DLC) for the investigation of undercut structures
on the base of CDR30-EBD tips. Such aggressive CD-AFM tip dimensions are mandatory to fulfill ITRS requirements
for the inspection of sub-28nm nodes, but are unattainable with state-of-art Si-based MEMS technologies today.
In addition to that, we demonstrate the ability of EBIP to realize field enhancement in sensor applications and the
fabrication of cold field emitters (CFE). For example: applying the EBIP approach allows for the production of CFEs,
which are characterized by considerably enhanced imaging resolution compared to standard thermal field emitters and
stable operation properties at room temperature without the need for periodic cathode flashing – unlike typical CFEs.
Based on these examples, we outline the strong capabilities of the EBIP approach to further downscale functional
structures in order to meet future demands in the semiconductor industry, and demonstrate its promising potential for the
development of advanced functionalities in the field of NEMS.
Atomic force microscopy (AFM) is increasingly used in the semiconductor industry as a versatile monitoring tool for highly critical lithography and etching process steps. Applications range from the inspection of the surface roughness of new materials, over accurate depth measurements to the determination of critical dimension structures. The aim to address the rapidly growing demands on measurement uncertainty and throughput more and more shifts the focus of attention to the AFM tip, which represents the crucial link between AFM tool and the sample to be monitored. Consequently, in order to reach the AFM tool’s full potential, the performance of the AFM tip has to be considered as a determining parameter. Currently available AFM tips made from silicon are generally limited by their diameter, radius, and sharpness, considerably restricting the AFM measurement capabilities on sub-30nm spaces. In addition to that, there’s lack of adequate characterization structures to accurately characterize sub-25nm tip diameters. Here, we present and discuss a recently introduced AFM tip design (T-shape like design) with precise tip diameters down to 15nm and tip radii down to 5nm fabricated from amorphous, high density diamond-like carbon (HDC/DLC) using electron beam induced processing (EBIP). In addition to that advanced design, we propose a new characterizer structure, which allows for accurate characterization and design control of sub-25nm tip diameters and sub-10nm tip edges radii. We demonstrate the potential advantages of combining a small tip shape design, i.e. tip diameter and tip edge radius, and an advanced tip characterizer for the semiconductor industry by the measurement of advanced lithography patterns.
KEYWORDS: Atomic force microscopy, Silicon, Scanning electron microscopy, Carbon, Semiconductors, Critical dimension metrology, Silicon carbide, Electron beams, Manufacturing, Process control
The demands on atomic force microscopy (AFM) as a reference technique for precisely determining surface properties
and structural designs of multiple patterns in the semiconductor industry are steadily increasing. With the aim to meet
ITRS requirements and simultaneously improve the accuracy of AFM-based critical dimension (CD) measurements at
constant resolution, the AFM tip more and more becomes a factor crucially determining the AFM performance. In this
context, AFM tip limitations are given by lack of sharpness with too large tip radii/diameter, insufficient wear resistance,
and high total cost, which does not conform to production environment needs.
One technical approach to overcome these tip limitations is provided by electron beam induced processing (EBIP), which
allows for manufacturing AFM tips of desired sharpness, shape, and mechanical stability. Here, we present T-shape-like
3D-AFM tips made of bulk amorphous, high density diamond-like carbon (HDC/DLC), and compare their performance
and wear resistance to standard silicon tips. We show the advantages of this approach for the semiconductor industry, in
particular on AFM3D technology in order to answer to sub-28 nm nodes requirements, and present tips with 15 nm
diameter at 10 nm vertical edge height.
Nanoemitters (NEs) are a promising replacement for electron sources in producing field emission CD-SEMs and CDTEMs.
So far, NEs have been fabricated by, e.g. carbon nanotubes or nanowhiskers of conductive materials. Here, we
present a new method to manufacture NEs using electron beam induced processing (EBIP) - a method well established in
the nanofabrication of super sharp probes for scanning probe microscopy - and show their unique performance. NEs
manufactured by EBIP combine a high density, diamond-like carbon core (HDC/DLC) with high aspect ratio and tip
sharpness, and a highly conductive coating. The EBIP process allows for the batch-fabrication of NEs at larger scales
with desired sharpness, shape, mechanical stability and conductivity. NEs, which can easily be mounted into existing
SEM/TEM assemblies, have been operated for > 5.000 h without any sign of degradation at a comparatively constant
beam current of 3 μA, wherein maximum current oscillations of 10% occurred, while current oscillations were less than
3% over a time span of several minutes. Due to the cold operating temperature and small tip radius, the resolution
improved up to 30% compared to a standard Schottky thermal field emitter. The improvement is significant in the low
voltage range below 5 kV.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.