Breaking Through the Process Development Barriers

by Dr. Dirk Ortloff

Dirk Ortloff1, Jens Popp1, Andreas Wagener1 and Kai Hahn2
1Process Relations GmbH
2University of Siegen Institute of Microsystem Technology
Corresponding author: dirk.ortloff@process-relations.com

Topics Covered

Abstract
Introduction
Possibilities for Software Support
XperiDesk
     XperiDesign
     XperiFication
     XperiLink
     XperiShare
Conclusions
References

Abstract

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 software suite.

Introduction

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 bases.

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.

Figure 1. 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.

XperiDesk

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 ramp-up.

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
  • XperiFication
  • XperiLink
  • XperiShare

XperiDesign

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 step editor.

Figure 2. Process step editor

XperiFication

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.

Figure 3. Results of a manufacturability assessment

XperiLink

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.

Figure 4. Viewing the data network build up by linking entities

XperiShare

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.

Conclusions

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.


References

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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Date Added: Jul 12, 2010 | Updated: Jun 11, 2013
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