Automated Metrology and Inspection
Optical inspection and metrology will continue to enable component manufacturers
to integrate metrology and yield-management strategies and reap the benefits of
cost-efficient, scalable production.
The 2001 downturn in telecommunications has significantly affected component manufacturers
and carriers alike. One result has been a substantial decrease in capital equipment
spending as companies position themselves for a period of slow sales.
Nevertheless, these same manufacturers continue
to invest in research and development, in yield management and in production efficiency.
Many are focusing their energies on developing cost-effective, high-yield production
systems to meet the needs of both current and next-generation networks. Their goal
is to achieve scalable component production that will support an inevitable return
Automation for higher yields
Metrology and inspection technologies are receiving,
and will continue to receive, much attention. Inefficient, manual techniques are
being upgraded to faster and more repeatable automated process-control systems that
can capture defects and provide early feedback for process improvement.
Despite the economic downturn, component manufacturers are investing
in automated inspection and metrology solutions. Here, automated optical defect
inspection identifies contamination on the surface of a laser diode.
Data from these automated systems integrate
the manufacturing process, tying upstream processes to downstream results. In other
industries, primarily data storage and semiconductor manufacturing, this move from
low-yield, fragmented processing to tightly linked, automated process flows boosted
yields four- to eightfold.
An example of this type of integration
is the use of automated optical inspection in the production of the laser diode
sources used in transmitter modules and as the pumps for erbium-doped fiber amplifier
modules. Automated optical inspection is supplanting traditional manual inspection
both for capturing surface defects and for measuring critical dimensions of the
waveguide ridge. Rules-based image analysis provides objective, quantitative evaluation
of device quality that can be used to adjust and improve prior processes.
With bar- and device-level serialization,
these optical inspection data may be tracked by part throughout the process. Automated
inspection stations, using the same software and protocols, may be employed at all
inspection steps. Therefore, early part conditions may be correlated with the final
performance to establish realistic, cost-appropriate process controls.
Companies also are gearing up for the production
of tomorrow’s network components. Updated metrology will control each new
For example, in the development of
components for 40-GHz and higher networks, chromatic and polarization mode dispersion
have an increasingly significant impact on the signal quality and bit error
rate. Manufacturers are working with metrology companies to develop all-parameter
testing that addresses both forms of dispersion as well as center wavelength, insertion
loss, reflected power, polarization-dependent loss and other parameters.
testing of a filter substrate for dense wavelength division multiplexing could account
for dispersion, center wavelength, polarization-dependent and insertion losses.
At the component level, there is a
move to integrate multiple components into single packages, thus reducing interconnect
losses and simplifying manufacturing. Here we are seeing parallels to the semiconductor
industry’s development of flip-chip and high-density interconnect packaging,
with more devices being completed on a wafer. Wafer-scale probe testing, metrology
and inspection will be employed more widely to capture defects and to measure the
performance of a device before the next manufacturing step.
An example of this type of wafer-level
processing is in the development of vertical-cavity surface-emitting lasers (VCSELs).
Unlike some other types of lasers, the VCSELs’ laser cavities are completed
on the wafer and, therefore, can be tested there. The ability to capture and eliminate
problems at the wafer level helps drive down costs to meet the required price points
in the cost-conscious metropolitan networking market.
Moreover, as networking technologies
continue to develop and mature, so will the methods for measuring and controlling
the quality of the components on which they are based. As they did for the semiconductor
and data storage industries, standards and standards-generating bodies will emerge
for optical component manufacturing, despite the disparity and sheer number of optical
devices being rapidly developed. Metrology professionals have the skill and knowledge
to help manufacturers establish these inspection standards and measurement protocols.
Meet the author
Michael Zecchino is marketing communications manager
at Veeco Metrology Group in Tucson, Ariz. He holds degrees in industrial engineering
from Pennsylvania State University in University Park and in English from the University
of Louisville in Kentucky.
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