Development of a fiber-optic based metrology
for nano/microscale mold filling
Majid Fazeli Jadidi*1, Maria Daniela Angione1, and Graham L.W. Cross1,2
ADAMA Innovations Limited, The Naughton Building, Trinity College Dublin, Dublin 2,Ireland1
Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Schoolof Physics, Trinity College Dublin, Dublin 2, Ireland2
E-mail: majid.fazeli@adamainnovations.com

Injection over-molding of polymeric material is a recent method in serial manufacturing ofoptic components in micro and nanoscale [1]. The advantages of injection molding
processing are: High throughput, ease of control of process parameters, low fabrication cost
and the wide flexibility of shapes that can be formed. Quality control during of a replication
process plays a key role in any micro-fabrication technology, and is the focus of this research.
The impact of the technology developed at Adama, in fundamentally enabling a rapid
prototype mold fabrication, is intended to drive disruptive innovation in several application
fields ranging from medical device microfluidics to optics. Micromachining, combined withDLC coating and subsequent nanostructuring (technology patented by Adama LLC) allows
creation of steel inserts which can be used for replication of thousands to hundreds ofthousands of polymer parts with functional nanofeatures. Adama has developed a two-steppatterning technology as a simple and efficient method to create micro and nanoscalefeatures. It is a resist-free, direct-write patterning technique for materials including diamondand DLC, for non-planar surfaces.
In-mold quality control as a key factor in serial replication process was targeted using fiberdelivered reflectance measurement. Our aim is to monitor the progress of filling process using
the fiber based measurement of scattering or reflection optical signals. While Time Resolved
Diffraction Scatterometry is a proven metrology for nanoimprint lithography, here we
propose Fiber-based interferometry as a nanoscopic mold-filling sensor for compatibility with
injection molding machinery. Fiber-Optic Interferometry is often used in high resolution
Atomic Force Microscopes (AFMs) to measure the deflection of cantilever. This system hasoutstanding sensitivity and allows measurement of displacements to sub-Angstrom levels.
Beams reflected from the fiber end-face and surface of target form an interference signal thatis monitored using signal photodiode. The change in power of interference signal can be
accurately converted to displacement in a calibrated system [2].
We have achieved preliminary results showing that the technique can measure the relative
motion of a polymeric sheet with nanometric precision. However, some challenges still
remain, the laboratory test results demonstrate the capability of this system to be used as moldfilling sensor.
Reference:[1] Sha, B.; Dimov, S.; Griffiths, C.; Packianather, M.S.; “Investigation of micro-injection
moulding: Factors affecting the replication quality” Journal of Materials Processing
Technology 2007, (183) 284–296.
[2] Oral, A.; Grimble, R.A.; Özer, H. Ö. and Pethica, J.B.; “High-sensitivity noncontact
atomic force microscope/scanning tunneling microscope (nc AFM/STM) operating at
subangstrom oscillation amplitudes for atomic resolution imaging and force spectroscopy”
Rev.of Sci. Inst. 2003, (74) 8.

a)b)Figure 1. Schematics of a) fiber delivered reflectance measurement for mold filling monitoring and b)
fiber-optic interferometer used for cantilever deflection detection in AFM [2].