Dirk Ortloff1, Jens Popp1,
Andreas Wagener1 and Kai Hahn2
1Process Relations GmbH
2University of Siegen Institute of Microsystem Technology
Corresponding author: [email protected]
Possibilities for Software Support
Development projects for new manufacturing recipes are challenged by a variety
of different external and internal requirements and constraints. This is especially
true when developing microelectromechanical systems (MEMS), nanoelectromechanical
systems (NEMS) or nano scale thin film devices and their specifically required
manufacturing processes. The diversity of technology options and their constraints
as well as the shrinking geometries and other external and internal forces put
the engineers and technologies to their limit.
To break through these barriers of growing complexity in fabrication process
development a new approach for adequate process design automation is necessary.
This approach needs to cover the design of new process sequences from the very
first idea to the final handover to mass production. It must also offer new
ground breaking solutions for the electronic transfer of process data and knowledge
to technology partners.
This paper presents such an approach by introducing the Process Development
Execution Systems (PDES). A PDES copes with the increasing development complexity
by offering a centralized collaboration platform supporting the process engineers
on their way through the development cycle. It gives a company a competitive
advantage by developing better solutions and providing shorter time-to-market.
The concepts for PDES have been researched in the EU Research project PROMENADE
(IST 507965) and are described in detail in its publications1-3.
The results of the project have become commercially available as the XperiDesk
Everybody occasionally has a "déjà vu". The term
describes a memory of an event that cannot be remembered clearly and is associated
with a current situation. Experiencing that special kind of blackouts is usually
not an issue, but it can be very unnerving while trying to solve a problem within
an engineering context. The "déjà vu problem" can
pose major challenges when developing new processes to manufacture micro-electromechanical
systems (MEMS), nano-electromechanical systems (NEMS), or other high-tech devices.
Every new product or product enhancement starts with a new idea. Experiences
gained by previous developments, scientific papers, and old lab-books provide
the major contribution to the realization of these new ideas. Some problems
are already encountered at these first stages of the product development: Colleagues
are not always available and lab-books are all too often only to those people
of value who wrote them. Even if the information is available in computer files,
they are in most cases distributed on several file servers or hidden in places
nobody will look at. Research papers can give great ideas, but the essential
part of the data is missing in most cases. So already in these first phases
of process developments good ideas are scrapped simply because there is no time
to perform the necessary research within the information sources and knowledge
However, this is only the beginning of the development endeavour. Adding external
obstacles like market forces, insufficient internal information and knowledge
management, limited development transparency, restricted virtual prototyping
possibilities, and missing electronic exchange make many development activities
daunting and expensive tasks. This leads to a repetition of experiments, which
is costly in terms of time, resources, and money. Experts in semiconductor process
development estimate that 10-15% of failed experiments could be prevented, if
previous results would be accessible in an easier way.
Possibilities for Software Support
After investigating the issues popping up when developing a feasible manufacturing
solution, it becomes clear that most of these problems are caused by the large
amount of data and the high degrees of parameter space. When the semiconductor
industry faced the problem of increasing layout complexity, the usage of electronic
design automation (EDA) software helped to overcome this problem. Similarly,
to address the hurdles highlighted in the introduction, a new software supported
development automation approach is required. This section will present topics,
where software can help with this task.
New ideas for process sequences are often based on or can benefit from previous
developments. Knowledge management software can provide ways to access these
previous development results in a structured manner. With such software, information
can be retrieved faster, and previous results can be found and thus used more
efficiently. Specialized software offers ways to view and search result data
(e.g., materials, process steps, machines and experiments) from different viewpoints,
to categorize data under different aspects, and to provide ways to link data
items together. Results and data that belong in the same context can be explored
in the resulting network and valuable information can be gained.
In the phase of assembling process steps to process sequences, software can
ease the assembly, storage and printing of new sequences. By providing access
to previously assembled process sequences, a designer can use these as building
blocks or modules in the newly developed sequence. The usage of standard building
blocks can drastically reduce design time and mistakes in the design phase.
In the verification phase, a software system shows its real advantages. Most
of the rules used have a form that can be expressed in a computer-readable way
(e.g., clean before deposition and do not exceed 150°C as long as a polymer
for lithography is deposited at the wafer). A domain expert can enter the rules
for his/her process steps and provides thus the rules for all engineers to check
the newly developed process sequences. This means a supporting software system
allows to manage rules, to connect rules with Boolean terms (i.e., and, or and
not) and to check process sequences using these rules.
However, this check gives no indication of the functionality or even the structure
of the produced device. Technology computer-aided design (TCAD) can provide
at least an idea about the produced structure. Most of these tools still need
experts to write the simulation description files, so they are currently not
always used to their full potential. To support these "virtual fabrication"
abilities to their full potential, a software system can manage simulation models
of different abstraction levels for process steps. It can provide support for
multiple models for multiple simulators per process step. If a simple model
is available for all basic process categories (e.g., deposition, etching and
lithography), the system is able to use the models for all process steps in
the process sequence and generate an input file for the desired simulator.
Currently simulation results are seen as standalone data. To rectify this situation,
a development infrastructure is able to manage the result files in combination
with the process sequence. This enables the engineer to compare the expected
results with the simulation results and with the real outcome. The knowledge
gained from the comparison can then be used to improve the simulation model.
After verification, the device is produced in an experimental fabrication environment.
In the first part of this phase, the infrastructure transfers the process sequence
to the fab environment. This is done by simply printing out a runcard for the
operators or by interfacing to the manufacturing execution system (MES) of the
fab. On the other hand, the system manages and documents last minute changes
to the sequence such as parameter adjustments in the fab. Additionally lot splits
and merges can be managed.
During and after processing, many measurements are done. These measurements
often produce files such as pictures or simple texts containing rows and columns
of data. A software system can manage these files, link related results together
and manage different versions of certain files (e.g., reports). Paired with
flexible text and graphical retrieval and search methods, a development support
system provides mechanisms to view and assess the accumulated data, information
and knowledge from different perspectives. It provides insight into previous
developments concerning information and time aspects.
Another important part of the data gathered during a development project is
the informal knowledge. It consists mostly of the discussions between engineers
about the experimental results. The development infrastructure channels and
archives this knowledge because it is of immeasurable value to future projects.
A great number of development activities in the industry are collaborative
efforts. This increases the need to exchange information between partners or
transfer process intellectual property (IP) from a vendor to a customer. Software
systems can support this transfer while being selective to protect the intellectual
property rights of the company3.
In summary, process development software systems can assist with the execution
of the development of new process sequences for new device architectures and
devices. These infrastructure tools support the whole development sequence -
from the first device idea to the transfer of the resulting recipe into production
or to a collaborating partner. Therefore, they close the development loop and
feed today's real world results into the ideas of tomorrow as depicted
in Figure 1. Software can never replace the creativity of engineers, but it
can help engineers to focus on good ideas and get rid of bad ideas early on.
PDES supported development cycle
Additionally, software can remove documentation and data collection burdens
by providing automated means for these purposes. Software systems also provide
a playground for engineers to test their ideas in a virtual fabrication environment,
providing ways to explore more ideas than previously possible. This way a development
support system gives a company a competitive advantage by developing better
solutions and providing shorter time-to-market.
As a new kind of software that provides the functionality described in this
section we introduce the Process Development Execution System (PDES) in this
paper. A PDES comprises a complete environment for all stages of process development
- from initial concept to final experimental success and transfer into
mass production. It provides a framework, which can be readily adapted to customer-specific
situations and procedures. The purpose of a Process Development Execution System
(PDES) is to manage and support the execution of development activities for
high-tech manufacturing processes.
A simplistic relational perspective is that a PDES is to the development of
high-tech manufacturing processes what a Manufacturing Execution System (MES)
is to the execution of volume production processes. The significant difference
between the two systems is that the emphasis of the PDES toolset is to deliver
enormous flexibility and experimentation freedom in a low volume environment,
while the tools of a MES focus on less variance, tighter controls, and logistics
in a high volume environment.
The similarities in purpose of a PDES and MES are the traditional common-ground
objectives of increasing traceability, productivity, and quality. With a PDES,
the expectation and objective is to increase the quality of the developed manufacturing
process, which is somewhat in contrast to the objective of improving production
quality with a MES.
The XperiDesk software suite is a leading edge, comprehensive application
for the development of complex manufacturing processes in the semiconductor
and thin-film MEMS device market. It supports process step and process sequence
development with innovative tools. One example is the customizable rules to
validate the compatibility and completeness requirements of process steps that
increase efficiency and integrity from the early concept stage to the final
However, the power of XperiDesk is even more apparent in its tools that provide
solutions for non-technical challenges. A few examples are internal and external
collaboration, documentation management and technology transfers, all of which
ease time-to-market pressures by truly expediting the development process. As
for subsequent developments, each can be progressively faster because XperiDesk
provides complete reuse of data and documentation from previous developments.
One of the innovative features of XperiDesk verifies the manufacturability
of a recipe before a live test. This is achieved by using customizable rules
to determine if the experiment could fail and/or damage equipment. An open interface
to integrate external simulation software enables efficient structural assessments
of designed devices. Robust tracking mechanisms support the management of all
instances of experimental and verification data as well as the execution of
iterative improvement steps.
XperiDesk not only solves the challenges of the ongoing increase in distributed
global development teams, it makes the degree of distributed collaboration transparent
and secure. A user/role security model, specifically designed for IPR protection
on a single item level, manages the distinct demarcations of various collaborations.
Another feature provides selective, mechanized, data exchange to collaborating
partners and customers while preserving the IP protection. The whole software
suite consists of four different modules, each focussing on one group of challenges:
XperiDesign supports the early concept stages of the process flow design.
It manages the data, information, and knowledge collected in the design phase
ranging from conversion of values in different units to the management of entire
process sequences. The power of this module increases with its use due to the
support for the reuse of already developed design elements. Design entities
can be arranged in multiple hierarchies and categories. Sophisticated inheritance
mechanisms permit the propagation of design properties and data for each entity
throughout the entire hierarchy structure. Figure 2 presents a view to process
Process step editor
XperiFication provides a two-tiered virtual assessment of newly created or
modified production recipes. The first tier assesses the manufacturability of
a recipe via a consistency check engine that uses customizable rules to evaluate
the compatibility requirements of process steps. Figure 3 presents an example
of such a check. The second tier level provides assessment via a combination
of an open interface to leverage existing TCAD-simulation tools and an interface
for Java Interpreter calculation models. XperiFication archives result files
in the underlying document management system, and the result files are accessible
from any client, since they are managed in the context of the sequence.
Results of a manufacturability assessment
XperiLink's supports the tracking of experimental verification results.
It auto-matically collects files, loads data from the file system, and provides
navigation and retrieval of data via multiple criteria searches, filters and
views. An example for one type of view is depicted in Figure 4. The data can
have multiple levels of detail to manage parameters, etc., with the added benefit
of viewing results from multiple per-spectives.
Viewing the data network build up by linking entities
XperiShare provides the selective, mechanized exchange of development data
between different partners. Selective export and import functionality allows
the bundling of IP packages and the transfer of various simulation and experimental
verification results. XperiShare increases the collaboration efficiency to achieve
an expedited fabrication ramp-up.
This paper gives a brief overview of current process development practices
and challenges with a focus on possible improvements using better software support.
It introduced the software category Process Development Execution Systems (PDES)
addressing the highlighted challenges. A PDES supports the whole development
flow - from the first device idea to the transfer of the resulting recipe
into production or to a collaborating partner. Therefore, it closes the development
loop and feeds today's real world results into the ideas of tomorrow.
This gives companies a competitive advantage by developing better solutions
and providing shorter time-to-market. Furthermore, the implementation of the
PDES concepts into the commercially available software suite XperiDesk is described.
1. A. Wagener, J. Popp K. Hahn, R. Brück;
Ortloff, D.: Process Design and Tracking Support for MEMS. In: Proceedings of
SPIE: Micromachining and Microfabrication Process Technology X, San Jose Bd.
6109, 2006. - Photonics West 2006
2. D. Ortloff, F. Cooijmans.; B. Veenstra:
A Systematic Approach Towards Reproducibility and Tracking of MEMS Process Development.
In: Proceedings of the 10th International Conference on the Commercialization
of Micro and Nano Systems, Baden-Baden, 2005. - COMS 2005
3. B. Veenstra, D. Ortloff, S. Langenhuisen:
An approach to exchange and generate knowledge of MEMS Process Development.
In: Proceedings of the 11th International Conference on the Commercialization
of Micro and Nano Systems, St. Petersburg, 2006. - COMS 2006
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