EMAMI AND BHANWAR SINGH (AMD Fellows, Advanced Micro Devices):
As feature sizes shrink below 90 nm, process tolerances have become
significantly tighter. Many tools
have not been able to keep up with the process control requirements
needed for 65-nm devices and beyond. The only way to tighten the tolerances
of these tools and processes is by integrating real-time metrology,
with the ultimate goal of achieving real-time process control—that
is, using the feedback from metrology sensors to control the tool during
processing. Run-to-run control measurement data, such as the fault-detection
mode, can be used to prevent processing or shut the tool down. In addition,
real-time measurement and feedback to the factory floor will help ensure
that learning rates are improved and wafer-sort yield variability is
metrology (IM) provides low-cost, in-line measurement capabilities.
It will play an important role for advanced processes, equipment control,
and tool-to-tool matching. Scatterometry will also be a critical technique.
Key IM applications in the 65-nm node and below will be for patterned
layers (CD, overlay, layer thickness, macrodefects), gate oxides (thickness,
uniformity, nitrogen content), metal layers (filling quality, grain
size, boundaries), and low-k materials (thickness, refractive index,
porosity, composition, uniformity).
the integration of metrology tools is progressing, standardized communication
interfaces for data transfer and networking must also be put in place.
Algorithms are needed for measurements, implementation, testing of integrated
measurement systems, and data management for seamless factory automation.
there have been major strides in accelerating this technology, it remains
a key challenge. The integration of these tools and the ability to provide
detection sensitivities between tool- and factory-level control systems
require a great deal of coordination and upfront, thorough planning
PASSOW (senior engineering manager, technology development and deployment,
IBM Systems and Technology Group): To continue with the current
trend in device scaling, manufacturing processes require more-exacting
controls. The proliferation of
such e-manufacturing control techniques relies on a critical concept–
effective system integration. Whether used for real-time feedback control
in the case of integrated metrology or remote access to troubleshoot
and repair a bottleneck process tool with e-diagnostics, the integration
challenge to successfully enable these and other mission-critical control
techniques is the ability to convert accurate data into useful information
in a timely manner.
design of the modern 300-mm fab operating in a "touchless"
(fully automated) manner is the most difficult of environments in which
to establish the appropriate infrastructure for hosting these controls.
This environment is designed to optimize development and manufacturing
activities with precision and speed. A typical fab has more than 200,000
wafer step moves in a day, gigabytes of data generated and analyzed,
and tens of thousands of statistical process control (SPC) charts updated,
all automatically. Advanced process control (APC) run-to-run calculations
are performed in a just-in-time manner with the most recently available
metrology data. IM devices supplement stand-alone measurement data for
real-time feedback control between wafers. To make this work without
humans involved, data quality and timeliness become paramount.
optimize a multitude of control schemes, the required data must
be available in a timely manner for use at the optimum location.
the factory level, the manufacturing execution system (MES) must manage
the execution of the thousands of operations in the factory simultaneously.
The factory-level systems for APC, fault detection and classification
(FDC), sensors, and SPC must be responsible for and direct the overall
control plans. At the tool level, embedded metrology, APC, FDC, sensors,
and SPC for local control are proliferating. Delegation of control activities
from the MES level to the embedded level is required to maintain consistent
performance of the factory in the automated, asynchronous environment.
Thus, cascading of control is needed between factory-level systems and
the localized control applications. To optimize a multitude of control
schemes effectively, the required data must be available in a timely
manner for use at the optimum location.
support the suite of embedded control solutions, the communications
infrastructure must be designed to support timely request-and-respond
functions. XML communication of commands, logistics information, and
data through a middleware layer is the most efficient and flexible implementation.
As the capabilities of the embedded controls increase, so does the need
for more efficient communication with the MES and other control applications.
Pushing Web-based techniques to the embedded layer strengthens and streamlines
the distributed nature of the open-architecture environment. Enhanced
data flow and increasingly complex data analysis techniques at the embedded
level drive the need for enhanced processing power at the embedded sensor,
PLC, or application level.
enable this functionality, which is desired in the advanced control
environment of the fully automated fab, strict adherence to standards
is required. Recipe management must address the need to integrate both
IM and APC recipes. Data collection and high-speed sensor communication
requirements must be addressed, along with the coordination of APC control
plans and IM sampling plans. Data must be in a standard format and accurately
time stamped. Data flow should be "fast enough" to meet application
needs with minimal latency. Control parameters should be flexible and
selectable, and process tools must universally accept real-time control
MADSEN (director of engineering, Nanometrics): As APC gains
widespread adoption, semiconductor manufacturers and process toolmakers
are coming under increasing pressure to provide fully integrated process
control solutions. The push for very tight process tolerances and productivity
improvements from the billion-plus-dollar factories drives the need
for APC. The ultimate goal of providing metrology directly on the process
tool—i.e., integrated metrology—is to enable closed-loop
control (CLC) of the process tool without operator intervention.
requirements for an IM module are considerably higher than for
a stand-alone metrology tool.
hot button issues are inherent with the introduction of IM as a solution
for tighter process tool control. Two important considerations are system
reliability and rapid/automatic tool recovery. Since metrology is an
integral part of the CLC system, the reliability requirements for the
IM module are considerably higher than for a stand-alone metrology tool.
Depending on how critical the CLC is to the process, an IM module failure
can result in the production line halting for several hours until service
is performed to correct the problem. A second issue is that, without
an operator monitoring the measurements in real time, if metrology system
performance degrades and is not detected early in the cycle, erroneous
information may be sent to the process tool. This can cause incorrect
changes in the process parameters, which in turn can result in catastrophic
misprocessing of product wafers.
solution to this problem is the routine performance of such system checks
as precision, stability, and accuracy on a periodic basis, which can
range from hours to days. In the case of thin-film and optical critical
dimension (OCD) metrology tools based on optical spectroscopy (reflectometry
or ellipsometry), wafers with standardized films or dimensional features
made of silicon dioxide and other stable materials are commonly used.
These precharacterized standards use highly accurate measurement systems
and are compared to standard reference materials.
performance of in-depth reference checks and calibration procedures
on the process tool is particularly disadvantageous in the case of IM,
since it requires the introduction of a standard or monitor wafer into
the tool. Obtaining monitor wafers from the fab stocking system and
loading them onto the IM module wastes both time and process tool resources.
better solution would be to implement a methodology that optimizes the
IM strategy for closed-loop control. There needs to be an approach that
minimizes interference with the process cycle, yet enables automatic
qualification of metrology system performance without the introduction
of a standard or monitor wafer into the process flow. This can be accomplished
using a reference standard located within the IM tool that can be easily
and automatically accessed by the tool without operator intervention.
this approach is implemented on each process tool, it opens a new way
of viewing the entire integrated metrology process. By using networking
software, correlations with other process tool calibration and reference
data can be performed. Questions such as why some process tools perform
better than others based on IM measurements (i.e., CD and film thickness)
can be easily answered. Autodiagnostics and autocalibration will enable
semiconductor and process tool manufacturers to manage their fabrication
processes without the need for operator intervention.
ASH (vice president of engineering, core products group, Advanced Energy):
Significant progress has been made in the industry toward improving
overall equipment effectiveness (OEE) through International Sematech
Manufacturing Initiative (ISMI) projects such as e-manufacturing and
standards programs. A significant gap, however, exists in the OEE strategy—namely,
the connectivity of critical subsystems such as RF generators, mass-flow
controllers, and other sensor-actuator devices into the overall fab
is calling for standard interfaces that allow seamless information flow,
resulting in higher OEE and reduced manufacturing costs. The focus has
been placed on SECS/GEM; interfaces A, B, and C; and infrastructure
standards such as the common equipment model (CEM). Unfortunately, efforts
have stopped just short of where they need to go. One look underneath
the hood of state-of-the-art 300-mm etch, CVD, and PVD plasma processing
tools demonstrates the lack of a standard information and control interface
at the critical subsystem layer. The hardware interfaces in use all
have proprietary software protocols.
has adopted a family of standards for this class of equipment—the
E54 Sensor/Actuator Network Standards. E54, however, is not driven as
a business requirement, and as a result, it is not followed. This standard
represents many years of work and industry experience, yet little if
any of this work is under consideration in the OEE strategy. The E54
subcommittee issued a consensus statement in the February 2005 North
American Standards meeting that documents this concern: "Tools
today are collecting and manipulating data internally utilizing E54
SEMI standard sensor bus technology. The equipment data acquisition
(EDA) standards within the SEMI CEM standard define mechanisms for extracting
data from equipment at high speeds for applications such as diagnostics
and fault detection. It is important that these two standards are aligned
so that sensor bus data collected internally could be easily exported
via the EDA interface. The best place to start in this alignment effort
might be extensions or changes to the CEM object model definition."
is not perfect, but it is a good starting point. In order to achieve
the productivity improvement called for in the OEE strategy, the industry
must first regard E54 and the information from the critical subsystems
as essential to e-manufacturing standards. Second, the industry must
drive to establish Ethernet as the single standard for network communications.
No industry can meet overall cost and quality objectives if the supply
chain is required to develop and support more than eight different complicated
network technologies with proprietary protocols.